Averages/Mode: Difference between revisions
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=={{header|Wren}}== |
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<lang wren>class Arithmetic { |
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static mode(arr) { |
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var map = {} |
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for (e in arr) { |
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if (map[e] == null) map[e] = 0 |
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map[e] = map[e] + 1 |
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} |
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var max = map.values.reduce {|x, y| x > y ? x : y} |
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return map.keys.where {|x| map[x] == max}.toList |
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} |
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} |
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System.print(Arithmetic.mode([1,2,3,4,5,5,51,2,3])) |
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</lang> |
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{{out}} |
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[2, 3, 5] |
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Order may differ |
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=={{header|XEmacs Lisp}}== |
=={{header|XEmacs Lisp}}== |
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Revision as of 11:03, 11 July 2016
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
Write a program to find the mode value of a collection.
The case where the collection is empty may be ignored. Care must be taken to handle the case where the mode is non-unique.
If it is not appropriate or possible to support a general collection, use a vector (array), if possible. If it is not appropriate or possible to support an unspecified value type, use integers.
ActionScript
This implementation does not work with arbitrary collections. However, it works with arrays containing mixed data, including strings and other arrays. <lang ActionScript>function Mode(arr:Array):Array { //Create an associative array to count how many times each element occurs, //an array to contain the modes, and a variable to store how many times each mode appears. var count:Array = new Array(); var modeList:Array; var maxCount:uint=0; for (var i:String in arr) { //Record how many times an element has occurred. Note that each element in the cuont array //has to be initialized explicitly, since it is an associative array. if (count[arr[i]]==undefined) { count[arr[i]]=1; } else { count[arr[i]]++; } //If this is now the most common element, clear the list of modes, and add this element. if(count[arr[i]] > maxCount) { maxCount=count[arr[i]]; modeList = new Array(); modeList.push(arr[i]); } //If this is a mode, add it to the list. else if(count[arr[i]] == maxCount){ modeList.push(arr[i]); } } return modeList; }</lang>
Ada
mode.ads: <lang Ada>generic
type Element_Type is private; type Element_Array is array (Positive range <>) of Element_Type;
package Mode is
function Get_Mode (Set : Element_Array) return Element_Array;
end Mode;</lang> mode.adb: <lang Ada>with Ada.Containers.Indefinite_Vectors;
package body Mode is
-- map Count to Elements
package Count_Vectors is new Ada.Containers.Indefinite_Vectors
(Element_Type => Element_Array,
Index_Type => Positive);
procedure Add (To : in out Count_Vectors.Vector; Item : Element_Type) is
use type Count_Vectors.Cursor;
Position : Count_Vectors.Cursor := To.First;
Found : Boolean := False;
begin
while not Found and then Position /= Count_Vectors.No_Element loop
declare
Elements : Element_Array := Count_Vectors.Element (Position);
begin
for I in Elements'Range loop
if Elements (I) = Item then
Found := True;
end if;
end loop;
end;
if not Found then
Position := Count_Vectors.Next (Position);
end if;
end loop;
if Position /= Count_Vectors.No_Element then
-- element found, remove it and insert to next count
declare
New_Position : Count_Vectors.Cursor :=
Count_Vectors.Next (Position);
begin
-- remove from old position
declare
Old_Elements : Element_Array :=
Count_Vectors.Element (Position);
New_Elements : Element_Array (1 .. Old_Elements'Length - 1);
New_Index : Positive := New_Elements'First;
begin
for I in Old_Elements'Range loop
if Old_Elements (I) /= Item then
New_Elements (New_Index) := Old_Elements (I);
New_Index := New_Index + 1;
end if;
end loop;
To.Replace_Element (Position, New_Elements);
end;
-- new position not already there?
if New_Position = Count_Vectors.No_Element then
declare
New_Array : Element_Array (1 .. 1) := (1 => Item);
begin
To.Append (New_Array);
end;
else
-- add to new position
declare
Old_Elements : Element_Array :=
Count_Vectors.Element (New_Position);
New_Elements : Element_Array (1 .. Old_Elements'Length + 1);
begin
New_Elements (1 .. Old_Elements'Length) := Old_Elements;
New_Elements (New_Elements'Last) := Item;
To.Replace_Element (New_Position, New_Elements);
end;
end if;
end;
else
-- element not found, add to count 1
Position := To.First;
if Position = Count_Vectors.No_Element then
declare
New_Array : Element_Array (1 .. 1) := (1 => Item);
begin
To.Append (New_Array);
end;
else
declare
Old_Elements : Element_Array :=
Count_Vectors.Element (Position);
New_Elements : Element_Array (1 .. Old_Elements'Length + 1);
begin
New_Elements (1 .. Old_Elements'Length) := Old_Elements;
New_Elements (New_Elements'Last) := Item;
To.Replace_Element (Position, New_Elements);
end;
end if;
end if;
end Add;
function Get_Mode (Set : Element_Array) return Element_Array is
Counts : Count_Vectors.Vector;
begin
for I in Set'Range loop
Add (Counts, Set (I));
end loop;
return Counts.Last_Element;
end Get_Mode;
end Mode;</lang> example use: <lang Ada>with Ada.Text_IO; with Mode; procedure Main is
type Int_Array is array (Positive range <>) of Integer; package Int_Mode is new Mode (Integer, Int_Array);
Test_1 : Int_Array := (1, 2, 3, 1, 2, 4, 2, 5, 2, 3, 3, 1, 3, 6); Result : Int_Array := Int_Mode.Get_Mode (Test_1);
begin
Ada.Text_IO.Put ("Input: ");
for I in Test_1'Range loop
Ada.Text_IO.Put (Integer'Image (Test_1 (I)));
if I /= Test_1'Last then
Ada.Text_IO.Put (",");
end if;
end loop;
Ada.Text_IO.New_Line;
Ada.Text_IO.Put ("Result:");
for I in Result'Range loop
Ada.Text_IO.Put (Integer'Image (Result (I)));
if I /= Result'Last then
Ada.Text_IO.Put (",");
end if;
end loop;
Ada.Text_IO.New_Line;
end Main;</lang>
- Output:
Input: 1, 2, 3, 1, 2, 4, 2, 5, 2, 3, 3, 1, 3, 6 Result: 2, 3
AutoHotkey
Search autohotkey.com: [1]
Source: AutoHotkey forum by Laszlo
<lang autohotkey>MsgBox % Mode("1 2 3")
MsgBox % Mode("1 2 0 3 0.0")
MsgBox % Mode("0.1 2.2 -0.1 0.22e1 2.20 0.1")
Mode(a, d=" ") { ; the number that occurs most frequently in a list delimited by d (space)
Sort a, ND%d%
Loop Parse, a, %d%
If (V != A_LoopField) {
If (Ct > MxCt)
MxV := V, MxCt := Ct
V := A_LoopField, Ct := 1
}
Else Ct++
Return Ct>MxCt ? V : MxV
}</lang>
AWK
<lang AWK>#!/usr/bin/gawk -f { # compute histogram histo[$1] += 1; };
function mode(HIS) {
# Computes the mode from Histogram A
max = 0;
n = 0;
for (k in HIS) {
val = HIS[k]; if (HIS[k] > max) { max = HIS[k];
n = 1;
List[n] = k; } else if (HIS[k] == max) { List[++n] = k; }
}
for (k=1; k<=n; k++) {
o = o""OFS""List[k];
}
return o;
}
END {
print mode(histo);
};</lang>
cat modedata.txt 0 3 6 aa 3 6 aa 3 aa 6 7 1 as@mini10:~/src/RosettaCode$ ./mode.awk modedata.txt 6 aa 3
BBC BASIC
<lang bbcbasic> DIM a(10), b(4)
a() = 1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17
b() = 1, 2, 4, 4, 1
DIM modes(10)
PRINT "Mode(s) of a() = " ;
FOR i% = 1 TO FNmodes(a(), modes())
PRINT ; modes(i%) " " ;
NEXT
PRINT
PRINT "Mode(s) of b() = " ;
FOR i% = 1 TO FNmodes(b(), modes())
PRINT ; modes(i%) " " ;
NEXT
PRINT
END
DEF FNmodes(a(), m())
LOCAL I%, J%, N%, c%(), max%
N% = DIM(a(),1)
IF N% = 0 THEN m(1) = a(0) : = 1
DIM c%(N%)
FOR I% = 0 TO N%-1
FOR J% = I%+1 TO N%
IF a(I%) = a(J%) c%(I%) += 1
NEXT
IF c%(I%) > max% max% = c%(I%)
NEXT I%
J% = 0
FOR I% = 0 TO N%
IF c%(I%) = max% J% += 1 : m(J%) = a(I%)
NEXT
= J%
</lang>
- Output:
Mode(s) of a() = 6 Mode(s) of b() = 1 4
C
Using an array of doubles. If another data type is desired, the cmp_dbl and vcount definitions should be changed accordingly.
<lang C>#include <stdio.h>
- include <stdlib.h>
typedef struct { double v; int c; } vcount;
int cmp_dbl(const void *a, const void *b) { double x = *(const double*)a - *(const double*)b; return x < 0 ? -1 : x > 0; }
int vc_cmp(const void *a, const void *b) { return ((const vcount*)b)->c - ((const vcount*)a)->c; }
int get_mode(double* x, int len, vcount **list) { int i, j; vcount *vc;
/* sort values */ qsort(x, len, sizeof(double), cmp_dbl);
/* count occurence of each value */ for (i = 0, j = 1; i < len - 1; i++, j += (x[i] != x[i + 1]));
*list = vc = malloc(sizeof(vcount) * j); vc[0].v = x[0]; vc[0].c = 1;
/* generate list value-count pairs */ for (i = j = 0; i < len - 1; i++, vc[j].c++) if (x[i] != x[i + 1]) vc[++j].v = x[i + 1];
/* sort that by count in descending order */ qsort(vc, j + 1, sizeof(vcount), vc_cmp);
/* the number of entries with same count as the highest */ for (i = 0; i <= j && vc[i].c == vc[0].c; i++);
return i; }
int main() { double values[] = { 1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 12, 12, 17 };
- define len sizeof(values)/sizeof(double)
vcount *vc;
int i, n_modes = get_mode(values, len, &vc);
printf("got %d modes:\n", n_modes); for (i = 0; i < n_modes; i++) printf("\tvalue = %g, count = %d\n", vc[i].v, vc[i].c);
free(vc); return 0; }</lang>
- Output:
got 2 modes:
value = 6, count = 4
value = 12, count = 4
C++
<lang cpp>#include <iterator>
- include <utility>
- include <algorithm>
- include <list>
- include <iostream>
// helper struct template<typename T> struct referring {
referring(T const& t): value(t) {}
template<typename Iter>
bool operator()(std::pair<Iter, int> const& p) const
{
return *p.first == value;
}
T const& value;
};
// requires: // FwdIterator is a ForwardIterator // The value_type of FwdIterator is EqualityComparable // OutIterator is an output iterator // the value_type of FwdIterator is convertible to the value_type of OutIterator // [first, last) is a valid range // provides: // the mode is written to result template<typename FwdIterator, typename OutIterator>
void mode(FwdIterator first, FwdIterator last, OutIterator result)
{
typedef typename std::iterator_traits<FwdIterator>::value_type value_type; typedef std::list<std::pair<FwdIterator, int> > count_type; typedef typename count_type::iterator count_iterator;
// count elements count_type counts;
while (first != last)
{
count_iterator element = std::find_if(counts.begin(), counts.end(),
referring<value_type>(*first));
if (element == counts.end())
counts.push_back(std::make_pair(first, 1));
else
++element->second;
++first;
}
// find maximum
int max = 0;
for (count_iterator i = counts.begin(); i != counts.end(); ++i)
if (i->second > max)
max = i->second;
// copy corresponding elements to output sequence
for (count_iterator i = counts.begin(); i != counts.end(); ++i)
if (i->second == max)
*result++ = *i->first;
}
// example usage int main() {
int values[] = { 1, 2, 3, 1, 2, 4, 2, 5, 2, 3, 3, 1, 3, 6 };
median(values, values + sizeof(values)/sizeof(int),
std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
return 0;
}</lang>
- Output:
2 3
C#
<lang csharp>using System; using System.Collections; using System.Collections.Generic; using System.Linq;
namespace Test {
class Program
{
static void Main(string[] args)
{
/*
* We Use Linq To Determine The Mode
*/
List<int> myList = new List<int>() { 1, 1, 2, 4, 4 };
var query = from numbers in myList //select the numbers
group numbers by numbers //group them together so we can get the count
into groupedNumbers
select new { Number = groupedNumbers.Key, Count = groupedNumbers.Count() }; //so we got a query
//find the max of the occurence of the mode
int max = query.Max(g => g.Count);
IEnumerable<int> modes = query.Where(x => x.Count == max).Select(x => x.Number);//match the frequence and select the number
foreach (var item in modes)
{
Console.WriteLine(item);
}
Console.ReadLine();
}
}
} </lang>
Clojure
<lang clojure>(defn modes [coll]
(let [distrib (frequencies coll)
[value freq] [first second] ; name the key/value pairs in the distrib (map) entries
sorted (sort-by (comp - freq) distrib)
maxfq (freq (first sorted))]
(map value (take-while #(= maxfq (freq %)) sorted))))</lang>
CoffeeScript
<lang coffeescript>mode = (arr) ->
# returns an array with the modes of arr, i.e. the
# elements that appear most often in arr
counts = {}
for elem in arr
counts[elem] ||= 0
counts[elem] += 1
max = 0
for key, cnt of counts
max = cnt if cnt > max
(key for key, cnt of counts when cnt == max)
console.log mode [1, 2, 2, 2, 3, 3, 3, 4, 4]</lang>
Common Lisp
The following returns a list of the modes of a sequence as the primary value, and the frequency as the secondary value. E.g., (mode '(a b c d a b c a b)) produces (A B) and 3. hash-table-options can be used to customize the hash table, e.g., to specify the test by which elements are compared.
<lang lisp>(defun mode (sequence &rest hash-table-options)
(let ((frequencies (apply #'make-hash-table hash-table-options)))
(map nil (lambda (element)
(incf (gethash element frequencies 0)))
sequence)
(let ((modes '())
(hifreq 0 ))
(maphash (lambda (element frequency)
(cond ((> frequency hifreq)
(setf hifreq frequency
modes (list element)))
((= frequency hifreq)
(push element modes))))
frequencies)
(values modes hifreq))))</lang>
D
The mode function returns a range of all the mode items: <lang d>import std.stdio, std.algorithm, std.array;
auto mode(T)(T[] items) pure /*nothrow @safe*/ {
int[T] aa;
foreach (item; items)
aa[item]++;
immutable m = aa.byValue.reduce!max;
return aa.byKey.filter!(k => aa[k] == m);
}
void main() /*@safe*/ {
auto data = [1, 2, 3, 1, 2, 4, 2, 5, 3, 3, 1, 3, 6];
writeln("Mode: ", data.mode);
data ~= 2;
writeln("Mode: ", data.mode);
}</lang>
- Output:
Mode: [3] Mode: [2, 3]
E
<lang e>pragma.enable("accumulator") def mode(values) {
def counts := [].asMap().diverge()
var maxCount := 0
for v in values {
maxCount max= (counts[v] := counts.fetch(v, fn{0}) + 1)
}
return accum [].asSet() for v => ==maxCount in counts { _.with(v) }
}</lang> <lang e>? mode([1,1,2,2,3,3,4,4,4,5,5,6,6,7,8,8,9,9,0,0,0])
- value: [4, 0].asSet()</lang>
In the line "maxCount max= (counts[v] := counts.fetch(v, fn{0}) + 1)", max= is an update-assignment operation like +=. (The parentheses are unnecessary.) A more verbose version would be:
<lang e> def newCount := counts.fetch(v, fn { 0 }) + 1
counts[v] := newCount maxCount := maxCount.max(newCount)</lang>
In for loops, each key and value from the collection are pattern matched against the specified key pattern => value pattern. In "for v => ==maxCount in counts", the == is a pattern-match operator which fails unless the value examined is equal to the specified value; so this selects only the input values (keys in counts) whose counts are equal to the maximum count.
EchoLisp
<lang scheme> (define (modes L) (define G (group* L)) ;; sorts and group equal items (define cardmax (for/max [(g G)] (length g))) (map first (filter (lambda(g) (= cardmax (length g))) G)))
(modes '( a b c a d e f))
→ (a)
(modes (iota 6))
→ (0 1 2 3 4 5)
(modes '(x))
→ (x)
(modes '(🎾 🏉 ☕️ 🎾 🎲 🎯 🎺 ☕️ 🎲 🎸 🎻 🏆 ☕️ 🏁 🎾 🎲 🎻 🏉 ))
→ (🎾 ☕️ 🎲)
(modes '()) 😖️ error: group : expected list : null 🔎 'modes' </lang>
Elena
<lang elena>#define system.
- define system'routines.
- define system'collections.
- define extensions.
- class(extension) op
{
#method mode
[
#var aCountMap := Dictionary new &default:0.
self run &each: anItem
[
aCountMap@anItem := aCountMap@anItem + 1.
].
aCountMap := aCountMap array_list sort:(:p:n) [ p > n ].
#var aMax := aCountMap firstMember.
^ aCountMap
filter &each:kv [ aMax safeEqual:kv ]
select &each:kv [ kv key ]
toArray.
]
}
- symbol program =
[
#var anArray1 := (1, 1, 2, 4, 4).
#var anArray2 := (1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17).
#var anArray3 := (1, "blue", 2, 7.5r, 5, "green", "red", 5, 2, "blue", "white").
console
writeLine:"mode of (":anArray1:") is (":(anArray1 mode):")"
writeLine:"mode of (":anArray2:") is (":(anArray2 mode):")"
writeLine:"mode of (":anArray3:") is (":(anArray3 mode):")".
]. </lang>
- Output:
mode of (1,1,2,4,4) is (4,1) mode of (1,3,6,6,6,6,7,7,12,12,17) is (6) mode of (1,blue,2,7.5,5,green,red,5,2,blue,white) is (5,2,blue)
Elixir
<lang elixir>defmodule Average do
def mode(list) do
gb = Enum.group_by(list, &(&1))
max = Enum.map(gb, fn {_,val} -> length(val) end) |> Enum.max
for {key,val} <- gb, length(val)==max, do: key
end
end
lists = [[3,1,4,1,5,9,2,6,5,3,5,8,9],
[1, 2, "qwe", "asd", 1, 2, "qwe", "asd", 2, "qwe"]]
Enum.each(lists, fn list ->
IO.puts "mode: #{inspect list}"
IO.puts " => #{inspect Average.mode(list)}"
end)</lang>
- Output:
mode: [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9] => [5] mode: [1, 2, "qwe", "asd", 1, 2, "qwe", "asd", 2, "qwe"] => [2, "qwe"]
Erlang
<lang Erlang> -module( mode ). -export( [example/0, values/1] ).
example() -> Set = [1, 2, "qwe", "asd", 1, 2, "qwe", "asd", 2, "qwe"], io:fwrite( "In ~p the mode(s) is(are): ~p~n", [Set, values(Set)] ).
values( Set ) -> Dict = lists:foldl( fun values_count/2, dict:new(), Set ), [X || {X, _Y} <- dict:fold( fun keep_maxs/3, [{0, 0}], Dict )].
keep_maxs( Key, Value, [{_Max_key, Max_value} | _] ) when Value > Max_value -> [{Key, Value}]; keep_maxs( Key, Value, [{_Max_key, Max_value} | _]=Maxs ) when Value =:= Max_value -> [{Key, Value} | Maxs]; keep_maxs( _Key, _Value, Maxs ) -> Maxs.
values_count( Value, Dict ) -> dict:update_counter( Value, 1, Dict ). </lang>
- Output:
12> mode:example(). In [1, 2, "qwe", "asd", 1, 2, "qwe", "asd", 2, "qwe"] the mode(s) is(are): ["qwe", 2]
ERRE
<lang ERRE>PROGRAM MODE_AVG
!$INTEGER
DIM A[10],B[10],Z[10]
PROCEDURE SORT(Z[],P->Z[])
LOCAL N,FLIPS
FLIPS=TRUE
WHILE FLIPS DO
FLIPS=FALSE
FOR N=0 TO P-1 DO
IF Z[N]>Z[N+1] THEN SWAP(Z[N],Z[N+1]) FLIPS=TRUE
END FOR
END WHILE
END PROCEDURE
PROCEDURE CALC_MODE(Z[],P->MODES$)
LOCAL I,OCCURRENCE,MAXOCCURRENCE,OLDVAL
SORT(Z[],P->Z[])
OCCURENCE=1
MAXOCCURENCE=0
OLDVAL=Z[0]
MODES$=""
FOR I=1 TO P DO
IF Z[I]=OLDVAL THEN
OCCURENCE=OCCURENCE+1
ELSE
IF OCCURENCE>MAXOCCURENCE THEN
MAXOCCURENCE=OCCURENCE
MODES$=STR$(OLDVAL)
ELSIF OCCURENCE=MAXOCCURENCE THEN
MODES$=MODES$+STR$(OLDVAL)
ELSE
!$NULL
END IF
OCCURENCE=1
END IF
OLDVAL=Z[I]
END FOR
!check after loop
IF OCCURENCE>MAXOCCURENCE THEN
MAXOCCURENCE=OCCURENCE
MODES$=STR$(OLDVAL)
ELSIF OCCURENCE=MAXOCCURENCE THEN
MODES$=MODES$+STR$(OLDVAL)
ELSE
!$NULL
END IF
END PROCEDURE
BEGIN
A[]=(1,3,6,6,6,6,7,7,12,12,17)
B[]=(1,2,4,4,1)
PRINT("Modes for array A (1,3,6,6,6,6,7,7,12,12,17)";)
CALC_MODE(A[],10->MODES$)
PRINT(MODES$)
PRINT("Modes for array B (1,2,4,4,1)";)
CALC_MODE(B[],4->MODES$)
PRINT(MODES$)
END PROGRAM</lang>
- Output:
Modes for array A (1,3,6,6,6,6,7,7,12,12,17) 6 Modes for array B (1,2,4,4,1) 1 4
Euphoria
<lang euphoria>include misc.e
function mode(sequence s)
sequence uniques, counts, modes
integer j,max
uniques = {}
counts = {}
for i = 1 to length(s) do
j = find(s[i], uniques)
if j then
counts[j] += 1
else
uniques = append(uniques, s[i])
counts = append(counts, 1)
end if
end for
max = counts[1]
for i = 2 to length(counts) do
if counts[i] > max then
max = counts[i]
end if
end for
j = 1
modes = {}
while j <= length(s) do
j = find_from(max, counts, j)
if j = 0 then
exit
end if
modes = append(modes, uniques[j])
j += 1
end while
return modes
end function
constant s = { 1, "blue", 2, 7.5, 5, "green", "red", 5, 2, "blue", "white" } pretty_print(1,mode(s),{3})</lang>
- Output:
{
"blue",
2,
5
}
F#
The Unchecked.defaultof became available in version 1.9.4 I think. <lang fsharp>let mode (l:'a seq) =
l
|> Seq.countBy (fun item -> item) // Count individual items
|> Seq.fold // Find max counts
(fun (cp, lst) (item, c) -> // State is (count, list of items with that count)
if c > cp then (c, [item]) // New max - keep count and a list of the single item
elif c = cp then (c, item :: lst) // New element with max count - prepend it to the list
else (cp,lst)) // else just keep old count/list
(0, [Unchecked.defaultof<'a>]) // Start with a count of 0 and a dummy item
|> snd // From (count, list) we just want the second item (the list)</lang>
Example usage: <lang fsharp>> mode ["a"; "b"; "c"; "c"];; val it : string list = ["c"] > mode ["a"; "b"; "c"; "c";"a"];; val it : string list = ["c"; "a"] > mode [1;2;1;3;2;0;0];; val it : int list = [0; 2; 1]</lang>
Factor
Factor has the word mode in math.statistics vocabulary.
<lang factor>{ 11 9 4 9 4 9 } mode ! 9 </lang>
Fortran
For the Qsort_Module see Sorting_algorithms/Quicksort#Fortran <lang fortran>program mode_test
use Qsort_Module only Qsort => sort implicit none
integer, parameter :: S = 10 integer, dimension(S) :: a1 = (/ -1, 7, 7, 2, 2, 2, -1, 7, -3, -3 /) integer, dimension(S) :: a2 = (/ 1, 1, 1, 1, 1, 0, 2, 2, 2, 2 /) integer, dimension(S) :: a3 = (/ 0, 0, -1, -1, 9, 9, 3, 3, 7, 7 /)
integer, dimension(S) :: o integer :: l, trash
print *, stat_mode(a1)
trash = stat_mode(a1, o, l) print *, o(1:l) trash = stat_mode(a2, o, l) print *, o(1:l) trash = stat_mode(a3, o, l) print *, o(1:l)
contains
! stat_mode returns the lowest (if not unique) mode ! others can hold other modes, if the mode is not unique ! if others is provided, otherslen should be provided too, and ! it says how many other modes are there. ! ok can be used to know if the return value has a meaning ! or the mode can't be found (void arrays) integer function stat_mode(a, others, otherslen, ok) integer, dimension(:), intent(in) :: a logical, optional, intent(out) :: ok integer, dimension(size(a,1)), optional, intent(out) :: others integer, optional, intent(out) :: otherslen
! ta is a copy of a, we sort ta modifying it, freq ! holds the frequencies and idx the index (for ta) so that ! the value appearing freq(i)-time is ta(idx(i)) integer, dimension(size(a, 1)) :: ta, freq, idx integer :: rs, i, tm, ml, tf
if ( present(ok) ) ok = .false.
select case ( size(a, 1) )
case (0) ! no mode... ok is false
return
case (1)
if ( present(ok) ) ok = .true.
stat_mode = a(1)
return
case default
if ( present(ok) ) ok = .true.
ta = a ! copy the array
call sort(ta) ! sort it in place (cfr. sort algos on RC)
freq = 1
idx = 0
rs = 1 ! rs will be the number of different values
do i = 2, size(ta, 1)
if ( ta(i-1) == ta(i) ) then
freq(rs) = freq(rs) + 1
else
idx(rs) = i-1
rs = rs + 1
end if
end do
idx(rs) = i-1
ml = maxloc(freq(1:rs), 1) ! index of the max value of freq
tf = freq(ml) ! the max frequency
tm = ta(idx(ml)) ! the value with that freq
! if we want all the possible modes, we provide others
if ( present(others) ) then
i = 1
others(1) = tm
do
freq(ml) = 0
ml = maxloc(freq(1:rs), 1)
if ( tf == freq(ml) ) then ! the same freq
i = i + 1 ! as the max one
others(i) = ta(idx(ml))
else
exit
end if
end do
if ( present(otherslen) ) then
otherslen = i
end if
end if
stat_mode = tm
end select
end function stat_mode
end program mode_test</lang>
Haskell
<lang haskell>import Prelude (foldr, maximum, (==), (+)) import Data.Map (insertWith', empty, filter, elems, keys)
mode :: (Ord a) => [a] -> [a] mode xs = keys (filter (== maximum (elems counts)) counts)
where counts = foldr (\x -> insertWith' (+) x 1) empty xs</lang>
counts is a map from each value found in xs to the number of occurrences (foldr traverses the list, insertWith' increments the count). This map is then filtered to only those entries whose count is the maximum count, and their keys (the values from the input list) are returned.
> mode [1,2,3,3,2,1,1] [1] > mode [1,2,3,3,2,1] [1,2,3]
Alternately: <lang haskell>import Data.List (group, sort)
mode :: (Ord a) => [a] -> [a] mode xs = map fst $ filter ((==best).snd) counts
where counts = map (\l -> (head l, length l)) . group . sort $ xs
best = maximum (map snd counts)</lang>
Another version that does not require an orderable type: <lang haskell>import Data.List (partition)
mode :: (Eq a) => [a] -> [a] mode = snd . modesWithCount
where modesWithCount :: (Eq a) => [a] -> (Int, [a])
modesWithCount [] = (0,[])
modesWithCount l@(x:_) | length xs > best = (length xs, [x])
| length xs < best = (best, modes)
| otherwise = (best, x:modes)
where (xs, notxs) = partition (== x) l
(best, modes) = modesWithCount notxs</lang>
GAP
<lang gap>mode := function(v)
local c, m; c := Collected(SortedList(v)); m := Maximum(List(c, x -> x[2])); return List(Filtered(c, x -> x[2] = m), y -> y[1]);
end;
mode([ 7, 5, 6, 1, 5, 5, 7, 12, 17, 6, 6, 5, 12, 3, 6 ]);
- [ 5, 6 ]</lang>
Go
Fixed collection type, fixed value type. In Go it is appropriate to program directly with built in types when possible. <lang go>package main
import "fmt"
func main() {
fmt.Println(mode([]int{2, 7, 1, 8, 2}))
fmt.Println(mode([]int{2, 7, 1, 8, 2, 8}))
}
func mode(a []int) []int {
m := make(map[int]int)
for _, v := range a {
m[v]++
}
var mode []int
var n int
for k, v := range m {
switch {
case v < n:
case v > n:
n = v
mode = append(mode[:0], k)
default:
mode = append(mode, k)
}
}
return mode
}</lang>
- Output:
[2] [2 8]
Fixed collection type, unspecified value type. An empty interface can hold any type. A slice []interface can hold a mix of types. It's not too much more source code, although there is some overhead to support this generality. <lang go>package main
import "fmt"
func main() {
fmt.Println(mode([]interface{}{.2, .7, .1, .8, .2}))
fmt.Println(mode([]interface{}{"two", 7, 1, 8, "two", 8}))
}
func mode(a []interface{}) []interface{} {
m := make(map[interface{}]int)
for _, v := range a {
m[v]++
}
var mode []interface{}
var n int
for k, v := range m {
switch {
case v < n:
case v > n:
n = v
mode = append(mode[:0], k)
default:
mode = append(mode, k)
}
}
return mode
}</lang>
- Output:
[0.2] [two 8]
General collection, fixed value type. The other kind of generality mentioned in the task requires more code. In Go this is done with an interface to define generalized collection methods. Here, the only method we need to demonstrate is iteration over the collection, so the interface has only one method. Any number of types then can implement the interface. Note that the mode function now takes an object of this interface type. In effect, it becomes a generic function, oblivious to the implementation of the collection, and accessing it only through its methods. <lang go>package main
import "fmt"
// interface type type intCollection interface {
iterator() func() (int, bool)
}
// concrete type implements interface type intSlice []int
// method on concrete type satisfies interface method func (s intSlice) iterator() func() (int, bool) {
i := 0
return func() (int, bool) {
if i >= len(s) {
return 0, false
}
v := s[i]
i++
return v, true
}
}
func main() {
fmt.Println(mode(intSlice{2, 7, 1, 8, 2}))
fmt.Println(mode(intSlice{2, 7, 1, 8, 2, 8}))
}
// mode is now a generic function, in a sense. // It knows what to do with an intCollection, // but does not know the underlying concrete type. func mode(a intCollection) []int {
m := make(map[int]int)
i := a.iterator()
for {
v, ok := i()
if !ok {
break
}
m[v]++
}
var mode []int
var n int
for k, v := range m {
switch {
case v < n:
case v > n:
n = v
mode = append(mode[:0], k)
default:
mode = append(mode, k)
}
}
return mode
}</lang>
- Output:
[2] [8 2]
General collection, unspecified value type, Finally, the two kinds of generality can be combined. The iterator returned by the interface method now returns an empty interface rather than an int. The intSlice concrete type of the previous example is retained, but now it must satisfy this interface method that uses interface{} instead of int. runeList is added to illustrate how multiple types can satisfy the same interface. <lang go>package main
import "fmt"
type collection interface {
iterator() func() (interface{}, bool)
}
type intSlice []int
func (s intSlice) iterator() func() (interface{}, bool) {
i := 0
return func() (interface{}, bool) {
if i >= len(s) {
return 0, false
}
v := s[i]
i++
return v, true
}
}
type runeList string
func (s runeList) iterator() func() (interface{}, bool) {
c := make(chan rune)
go func() {
for _, r := range s {
c <- r
}
close(c)
}()
return func() (interface{}, bool) {
r, ok := <-c
return string(r), ok
}
}
func main() {
fmt.Println(mode(intSlice{2, 7, 1, 8, 2}))
fmt.Println(mode(runeList("Enzyklopädie")))
}
func mode(a collection) []interface{} {
m := make(map[interface{}]int)
i := a.iterator()
for {
v, ok := i()
if !ok {
break
}
m[v]++
}
var mode []interface{}
var n int
for k, v := range m {
switch {
case v < n:
case v > n:
n = v
mode = append(mode[:0], k)
default:
mode = append(mode, k)
}
}
return mode
}</lang>
- Output:
("Enzyklopädie" has no repeated letters. All are modal.)
[2] [e d i k l o n p y z E ä]
Groovy
Solution, both "collection type" and "element type" agnostic: <lang groovy>def mode(Iterable col) {
assert col
def m = [:]
col.each {
m[it] = m[it] == null ? 1 : m[it] + 1
}
def keys = m.keySet().sort { -m[it] }
keys.findAll { m[it] == m[keys[0]] }
}</lang> Test: <lang groovy>def random = new Random() def sourceList = [ 'Lamp', 42.0, java.awt.Color.RED, new Date(), ~/pattern/] (0..10).each {
def a = (0..10).collect { sourceList[random.nextInt(5)] }
println "${mode(a)} == mode(${a})"
}</lang>
- Output:
[pattern] == mode([pattern, pattern, pattern, Lamp, pattern, Fri Oct 28 23:43:20 CDT 2011, java.awt.Color[r=255,g=0,b=0], Lamp, Lamp, Lamp, pattern]) [Lamp] == mode([Lamp, Fri Oct 28 23:43:20 CDT 2011, Lamp, java.awt.Color[r=255,g=0,b=0], 42.0, java.awt.Color[r=255,g=0,b=0], Fri Oct 28 23:43:20 CDT 2011, Lamp, pattern, pattern, 42.0]) [java.awt.Color[r=255,g=0,b=0]] == mode([java.awt.Color[r=255,g=0,b=0], java.awt.Color[r=255,g=0,b=0], 42.0, 42.0, Fri Oct 28 23:43:20 CDT 2011, Fri Oct 28 23:43:20 CDT 2011, 42.0, java.awt.Color[r=255,g=0,b=0], pattern, pattern, java.awt.Color[r=255,g=0,b=0]]) [Fri Oct 28 23:43:20 CDT 2011] == mode([Fri Oct 28 23:43:20 CDT 2011, pattern, 42.0, Fri Oct 28 23:43:20 CDT 2011, Lamp, pattern, Fri Oct 28 23:43:20 CDT 2011, java.awt.Color[r=255,g=0,b=0], 42.0, 42.0, Fri Oct 28 23:43:20 CDT 2011]) [Fri Oct 28 23:43:20 CDT 2011, Lamp] == mode([42.0, Fri Oct 28 23:43:20 CDT 2011, Lamp, Lamp, Fri Oct 28 23:43:20 CDT 2011, Fri Oct 28 23:43:20 CDT 2011, 42.0, Lamp, java.awt.Color[r=255,g=0,b=0], Lamp, Fri Oct 28 23:43:20 CDT 2011]) [java.awt.Color[r=255,g=0,b=0]] == mode([Fri Oct 28 23:43:20 CDT 2011, java.awt.Color[r=255,g=0,b=0], java.awt.Color[r=255,g=0,b=0], pattern, 42.0, java.awt.Color[r=255,g=0,b=0], java.awt.Color[r=255,g=0,b=0], 42.0, pattern, Fri Oct 28 23:43:20 CDT 2011, pattern]) [42.0, java.awt.Color[r=255,g=0,b=0]] == mode([42.0, java.awt.Color[r=255,g=0,b=0], pattern, Fri Oct 28 23:43:20 CDT 2011, Lamp, java.awt.Color[r=255,g=0,b=0], Lamp, Fri Oct 28 23:43:20 CDT 2011, java.awt.Color[r=255,g=0,b=0], 42.0, 42.0]) [Fri Oct 28 23:43:20 CDT 2011] == mode([java.awt.Color[r=255,g=0,b=0], pattern, Fri Oct 28 23:43:20 CDT 2011, Lamp, 42.0, Fri Oct 28 23:43:20 CDT 2011, Fri Oct 28 23:43:20 CDT 2011, pattern, java.awt.Color[r=255,g=0,b=0], Lamp, Fri Oct 28 23:43:20 CDT 2011]) [Fri Oct 28 23:43:20 CDT 2011] == mode([Fri Oct 28 23:43:20 CDT 2011, pattern, Fri Oct 28 23:43:20 CDT 2011, java.awt.Color[r=255,g=0,b=0], pattern, Fri Oct 28 23:43:20 CDT 2011, 42.0, java.awt.Color[r=255,g=0,b=0], Lamp, Fri Oct 28 23:43:20 CDT 2011, 42.0]) [pattern] == mode([42.0, pattern, pattern, Lamp, 42.0, Lamp, Fri Oct 28 23:43:20 CDT 2011, java.awt.Color[r=255,g=0,b=0], pattern, 42.0, pattern]) [Lamp, 42.0] == mode([Fri Oct 28 23:43:20 CDT 2011, pattern, Lamp, Lamp, Lamp, java.awt.Color[r=255,g=0,b=0], Fri Oct 28 23:43:20 CDT 2011, 42.0, 42.0, pattern, 42.0])
Icon and Unicon
The mode procedure generates all n mode values if the collection is n-modal. <lang icon>procedure main(args)
every write(!mode(args))
end
procedure mode(A)
hist := table(0)
every hist[!A] +:= 1
hist := sort(hist, 2)
modeCnt := hist[*hist][2]
every modeP := hist[*hist to 1 by -1] do {
if modeCnt = modeP[2] then suspend modeP[1]
else fail
}
end</lang>
- Sample outputs:
->am 3 1 4 1 5 9 7 6 1 ->am 3 1 4 1 5 9 7 6 3 3 1 ->
J
<lang j>mode=: ~. #~ ( = >./ )@( #/.~ )</lang> Example:
mode 1 1 2 2 3 3 4 4 4 5 5 6 6 7 8 8 9 9 0 0 0 4 0
Java
<lang java>import java.util.*;
public class Mode {
public static <T> List<T> mode(List<? extends T> coll) {
Map<T, Integer> seen = new HashMap<T, Integer>();
int max = 0;
List<T> maxElems = new ArrayList<T>();
for (T value : coll) {
if (seen.containsKey(value))
seen.put(value, seen.get(value) + 1);
else
seen.put(value, 1);
if (seen.get(value) > max) {
max = seen.get(value);
maxElems.clear();
maxElems.add(value);
} else if (seen.get(value) == max) {
maxElems.add(value);
}
}
return maxElems;
}
public static void main(String[] args) {
System.out.println(mode(Arrays.asList(1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17))); // prints [6]
System.out.println(mode(Arrays.asList(1, 1, 2, 4, 4))); // prints [1, 4]
}
}</lang>
JavaScript
<lang javascript>function mode(ary) {
var counter = {};
var mode = [];
var max = 0;
for (var i in ary) {
if (!(ary[i] in counter))
counter[ary[i]] = 0;
counter[ary[i]]++;
if (counter[ary[i]] == max)
mode.push(ary[i]);
else if (counter[ary[i]] > max) {
max = counter[ary[i]];
mode = [ary[i]];
}
}
return mode;
}
mode([1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]); // [6] mode([1, 2, 4, 4, 1]); // [1,4]</lang>
jq
jq only supports hashing of strings, so to preserve generality -- that is, to avoid assuming anything about the input array -- we simply sort it. jq's sort is very fast in any case.<lang jq># modes/0 produces an array of [value, count]
- in increasing order of count:
def modes:
sort | reduce .[] as $i ([]; # state variable is an array of [value, count] if length == 0 then [ [$i, 1] ] elif .[-1][0] == $i then setpath([-1,1]; .[-1][1] + 1) else . + $i,1 end ) | sort_by( .[1] );
- mode/0 outputs a stream of the modal values;
- if the input array is empty, the output stream is also empty.
def mode:
if length == 0 then empty
else modes as $modes
| $modes[-1][1] as $count
| $modes[] | select( .[1] == $count) | .[0]
end;</lang>Examples:<lang jq>
[1,2,3,1,2,1] | mode # => 1 [1,2,3,1,2,1,2] | mode # => 1 2 [1.1, 1.2, 1.3, 1.1, 1.2, 1.1] | mode) # => 1.1</lang>
Julia
<lang k>function modes(values)
dict = Dict() # Values => Number of repetitions modesArray = typeof(values[1])[] # Array of the modes so far max = 0 # Max of repetitions so far
for v in values
# Add one to the dict[v] entry (create one if none)
if v in keys(dict)
dict[v] += 1
else
dict[v] = 1
end
# Update modesArray if the number of repetitions
# of v reaches or surpasses the max value
if dict[v] >= max
if dict[v] > max
empty!(modesArray)
max += 1
end
append!(modesArray, [v])
end
end
return modesArray
end
println(modes([1,3,6,6,6,6,7,7,12,12,17])) println(modes((1,1,2,4,4)))</lang>
K
<lang k> mode: {(?x)@&n=|/n:#:'=x}
mode 1 1 1 1 2 2 2 3 3 3 3 4 4 3 2 4 4 4
3 4</lang>
Lasso
<lang Lasso>define getmode(a::array)::array => { local(mmap = map, maxv = 0, modes = array) // store counts with e in #a do => { #mmap->keys >> #e ? #mmap->find(#e) += 1 | #mmap->insert(#e = 1) } // get max value with e in #mmap->keys do => { #mmap->find(#e) > #maxv ? #maxv = #mmap->find(#e) } // get modes with max value with e in #mmap->keys where #mmap->find(#e) == #maxv do => { #modes->insert(#e) } return #modes } getmode(array(1,3,6,6,6,6,7,7,12,12,17)) getmode(array(1,3,6,3,4,8,9,1,2,3,2,2))</lang>
- Output:
array(6) array(2, 3)
Liberty BASIC
Using string of integers instead collection. <lang lb> a$ = "1 3 6 6 6 6 7 7 12 12 17" b$ = "1 2 4 4 1"
print "Modes for ";a$ print modes$(a$) print "Modes for ";b$ print modes$(b$)
function modes$(a$) 'get array size
n=0
t$ = "*"
while t$<>""
n=n+1
t$=word$(a$, n)
'print n, t$
wend
n=n-1
'print "n=", n
'dim array 'read in array
redim a(n)
for i = 1 to n
a(i)=val(word$(a$, i))
'print i, a(i)
next
'sort
sort a(), 1, n
'get the modes
occurence = 1
maxOccurence = 0
oldVal = a(1)
modes$ = ""
for i = 2 to n
'print i, a(i)
if a(i) = oldVal then
occurence = occurence + 1
else
select case
case occurence > maxOccurence
maxOccurence = occurence
modes$ = oldVal; " "
case occurence = maxOccurence
modes$ = modes$; oldVal; " "
end select
occurence = 1
end if
oldVal = a(i)
next
'check after loop
select case
case occurence > maxOccurence
maxOccurence = occurence
modes$ = oldVal; " "
case occurence = maxOccurence
modes$ = modes$; oldVal; " "
end select
end function </lang>
- Output:
Modes for 1 3 6 6 6 6 7 7 12 12 17 6 Modes for 1 2 4 4 1 1 4
Lua
<lang lua>function mode (numlist)
if type(numlist) ~= 'table' then return numlist end
local sets = {}
local mode
local modeValue = 0
table.foreach(numlist,function(i,v) if sets[v] then sets[v] = sets[v] + 1 else sets[v] = 1 end end)
for i,v in next,sets do
if v > modeValue then
modeValue = v
mode = i
else
if v == modeValue then
if type(mode) == 'table' then
table.insert(mode,i)
else
mode = {mode,i}
end
end
end
end
return mode
end
result = mode({1,3,6,6,6,6,7,7,12,12,17}) print(result) result = mode({1, 1, 2, 4, 4}) if type(result) == 'table' then
for i,v in next,result do io.write(v..' ') end print ()
end</lang>
Maple
The built-in function Statistics:-Mode can be used to compute a mode. When the mode is unique, it returns a numeric result and when there are multiple modes, it returns a set, as in the following example: <lang Maple>Statistics:-Mode([1, 2.1, 2.1, 3]); Statistics:-Mode([1, 2.1, 2.1, 3.2, 3.2, 5]);</lang>
- Output:
2.1
{2.1, 3.2}
Mathematica / Wolfram Language
Built-in function commonest returns a list of the most common element(s), even is there is only one 'commonest' number. Example for multiple 'commonest' numbers and a single 'commonest' number: <lang Mathematica> Commonest[{b, a, c, 2, a, b, 1, 2, 3}]
Commonest[{1, 3, 2, 3}]</lang>
- Output:
{b,a,2}
{3}
MATLAB
<lang Matlab>function modeValue = findmode(setOfValues)
modeValue = mode(setOfValues);
end</lang>
MUMPS
<lang MUMPS>MODE(X)
;X is assumed to be a list of numbers separated by "^" ;I is a loop index ;L is the length of X ;Y is a new array ;ML is the list of modes ;LOC is a placeholder to shorten the statement Q:'$DATA(X) "No data" Q:X="" "Empty Set" NEW Y,I,L,LOC SET L=$LENGTH(X,"^"),ML="" FOR I=1:1:L SET LOC=+$P(X,"^",I),Y(LOC)=$S($DATA(Y(LOC)):Y(LOC)+1,1:1) SET I="",I=$O(Y(I)),ML=I ;Prime the pump, rather than test for no data FOR S I=$O(Y(I)) Q:I="" S ML=$SELECT(Y($P(ML,"^"))>Y(I):ML,Y($P(ML,"^"))<Y(I):I,Y($P(ML,"^"))=Y(I):ML_"^"_I) QUIT ML</lang>
USER>W $$MODE^ROSETTA("1^2^3^2")
2
USER>W $$MODE^ROSETTA("1^2^3^2^3")
2^3
USER>W $$MODE^ROSETTA("")
Empty Set
NetRexx
<lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols nobinary
run_samples() return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method mode(lvector = java.util.List) public static returns java.util.List
seen = 0
modes =
modeMax = 0
loop v_ = 0 to lvector.size() - 1
mv = Rexx lvector.get(v_)
seen[mv] = seen[mv] + 1
select
when seen[mv] > modeMax then do
modeMax = seen[mv]
modes =
nx = 1
modes[0] = nx
modes[nx] = mv
end
when seen[mv] = modeMax then do
nx = modes[0] + 1
modes[0] = nx
modes[nx] = mv
end
otherwise do
nop
end
end
end v_
modeList = ArrayList(modes[0]) loop v_ = 1 to modes[0] val = modes[v_] modeList.add(val) end v_
return modeList
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method mode(rvector = Rexx[]) public static returns java.util.List
return mode(ArrayList(Arrays.asList(rvector)))
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method show_mode(lvector = java.util.List) public static returns java.util.List
modes = mode(lvector) say 'Vector:' (Rexx lvector).space(0)', Mode(s):' (Rexx modes).space(0) return modes
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method show_mode(rvector = Rexx[]) public static returns java.util.List
return show_mode(ArrayList(Arrays.asList(rvector)))
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method run_samples() public static
show_mode([Rexx 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]) -- 10 9 8 7 6 5 4 3 2 1 show_mode([Rexx 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0, 0.11]) -- 0 show_mode([Rexx 30, 10, 20, 30, 40, 50, -100, 4.7, -11e+2]) -- 30 show_mode([Rexx 30, 10, 20, 30, 40, 50, -100, 4.7, -11e+2, -11e+2]) -- 30 -11e2 show_mode([Rexx 1, 8, 6, 0, 1, 9, 4, 6, 1, 9, 9, 9]) -- 9 show_mode([Rexx 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]) -- 1 2 3 4 5 6 7 8 9 10 11 show_mode([Rexx 8, 8, 8, 2, 2, 2]) -- 8 2 show_mode([Rexx 'cat', 'kat', 'Cat', 'emu', 'emu', 'Kat']) -- emu show_mode([Rexx 0, 1, 2, 3, 3, 3, 4, 4, 4, 4, 1, 0]) -- 4 show_mode([Rexx 2, 7, 1, 8, 2]) -- 2 show_mode([Rexx 2, 7, 1, 8, 2, 8]) -- 8 2 show_mode([Rexx 'E', 'n', 'z', 'y', 'k', 'l', 'o', 'p', 'ä', 'd', 'i', 'e']) -- E n z y k l o p ä d i e show_mode([Rexx 'E', 'n', 'z', 'y', 'k', 'l', 'o', 'p', 'ä', 'd', 'i', 'e', 'ä']) -- ä show_mode([Rexx 3, 1, 4, 1, 5, 9, 7, 6]) -- 1 show_mode([Rexx 3, 1, 4, 1, 5, 9, 7, 6, 3]) -- 3, 1 show_mode([Rexx 1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]) -- 6 show_mode([Rexx 1, 1, 2, 4, 4]) -- 4 1 return
</lang> Output:
Vector: [10,9,8,7,6,5,4,3,2,1], Mode(s): [10,9,8,7,6,5,4,3,2,1] Vector: [10,9,8,7,6,5,4,3,2,1,0,0,0,0,0.11], Mode(s): [0] Vector: [30,10,20,30,40,50,-100,4.7,-1100], Mode(s): [30] Vector: [30,10,20,30,40,50,-100,4.7,-1100,-1100], Mode(s): [30,-1100] Vector: [1,8,6,0,1,9,4,6,1,9,9,9], Mode(s): [9] Vector: [1,2,3,4,5,6,7,8,9,10,11], Mode(s): [1,2,3,4,5,6,7,8,9,10,11] Vector: [8,8,8,2,2,2], Mode(s): [8,2] Vector: [cat,kat,Cat,emu,emu,Kat], Mode(s): [emu] Vector: [0,1,2,3,3,3,4,4,4,4,1,0], Mode(s): [4] Vector: [2,7,1,8,2], Mode(s): [2] Vector: [2,7,1,8,2,8], Mode(s): [2,8] Vector: [E,n,z,y,k,l,o,p,ä,d,i,e], Mode(s): [E,n,z,y,k,l,o,p,ä,d,i,e] Vector: [E,n,z,y,k,l,o,p,ä,d,i,e,ä], Mode(s): [ä] Vector: [3,1,4,1,5,9,7,6], Mode(s): [1] Vector: [3,1,4,1,5,9,7,6,3], Mode(s): [1,3] Vector: [1,3,6,6,6,6,7,7,12,12,17], Mode(s): [6] Vector: [1,1,2,4,4], Mode(s): [1,4]
Nim
<lang nim>import tables
proc modes[T](xs: openArray[T]): T =
var count = initCountTable[T]() for x in xs: count.inc(x) largest(count).key
echo modes(@[1,3,6,6,6,6,7,7,12,12,17]) echo modes(@[1,1,2,4,4])</lang> Output:
6 1
Oberon-2
<lang oberon2> MODULE Mode; IMPORT
Object:Boxed, ADT:Dictionary, ADT:LinkedList, Out := NPCT:Console;
TYPE
Key = Boxed.LongInt; Val = Boxed.LongInt;
VAR
x: ARRAY 11 OF LONGINT; y: ARRAY 5 OF LONGINT; z: ARRAY 8 OF LONGINT;
PROCEDURE Show(ll: LinkedList.LinkedList(Key));
VAR
iter: LinkedList.Iterator(Key);
i: LONGINT;
k: Key;
BEGIN
iter := ll.GetIterator(NIL);
FOR i := 0 TO ll.Size() - 1 DO;
k := iter.Next();
Out.Int(k.value,0);Out.Ln;
END;
END Show;
PROCEDURE Mode(x: ARRAY OF LONGINT): LinkedList.LinkedList(Key);
VAR
d: Dictionary.Dictionary(Key,Val);
i: LONGINT;
k: Key; v: Val;
iter: Dictionary.IterKeys(Key,Val);
resp: LinkedList.LinkedList(Key);
max: Boxed.LongInt;
BEGIN
d := NEW(Dictionary.Dictionary(Key,Val));
FOR i := 0 TO LEN(x) - 1 DO
k := NEW(Key,x[i]);
IF d.Lookup(k,v) THEN
d.Set(k,NEW(Val,v.value + 1));
ELSE
d.Set(k,NEW(Val,1))
END
END;
max := NEW(Boxed.LongInt,0);
resp := NEW(LinkedList.LinkedList(Key));
iter := d.IterKeys();
WHILE (iter.Next(k)) DO
v := d.Get(k);
IF v.Cmp(max) > 0 THEN
resp.Clear();
resp.Append(k);max := v
ELSIF v.Cmp(max) = 0 THEN
resp.Append(k);max := v
END
END;
RETURN resp
END Mode;
BEGIN
x[0] := 1; x[1] := 3; x[2] := 6; x[3] := 6; x[4] := 6; x[5] := 6; x[6] := 7; x[7] := 7; x[8] := 12; x[9] := 12; x[10] := 17; Show(Mode(x));Out.Ln; y[0] := 1; y[1] := 2; y[2] := 4; y[3] := 4; y[4] := 1; Show(Mode(y));Out.Ln; z[0] := 1; z[1] := 2; z[2] := 4; z[3] := 4; z[4] := 1; z[5] := 5; z[6] := 5; z[7] := 5; Show(Mode(z));Out.Ln;
END Mode. </lang> {{out}
6 4 1 5
Objeck
<lang objeck> use Collection;
class Mode {
function : Main(args : String[]) ~ Nil {
Print(Mode([1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]));
Print(Mode([1, 2, 4, 4, 1]));
}
function : Mode(coll : Int[]) ~ IntVector {
seen := IntMap->New();
max := 0;
maxElems := IntVector->New();
each(i : coll) {
value := coll[i];
featched := seen->Find(value)->As(IntHolder);
if(featched <> Nil) {
seen->Remove(value);
seen->Insert(value, IntHolder->New(featched->Get() + 1));
}
else {
seen->Insert(value, IntHolder->New(1));
};
featched := seen->Find(value)->As(IntHolder);
if(featched->Get() > max) {
max := featched->Get();
maxElems->Empty();
maxElems->AddBack(value);
}
else if(featched->Get() = max) {
maxElems->AddBack(value);
};
};
return maxElems; }
function : Print(out : IntVector) ~ Nil {
'['->Print();
each(i : out) {
out->Get(i)->Print();
if(i + 1 < out->Size()) {
", "->Print();
};
};
']'->PrintLine();
}
} </lang>
Objective-C
<lang objc>#import <Foundation/Foundation.h>
@interface NSArray (Mode) - (NSArray *)mode; @end
@implementation NSArray (Mode) - (NSArray *)mode {
NSCountedSet *seen = [NSCountedSet setWithArray:self];
int max = 0;
NSMutableArray *maxElems = [NSMutableArray array];
for ( obj in seen ) {
int count = [seen countForObject:obj];
if (count > max) {
max = count;
[maxElems removeAllObjects];
[maxElems addObject:obj];
} else if (count == max) {
[maxElems addObject:obj];
}
}
return maxElems;
} @end</lang>
OCaml
<lang ocaml>let mode lst =
let seen = Hashtbl.create 42 in
List.iter (fun x ->
let old = if Hashtbl.mem seen x then
Hashtbl.find seen x
else 0 in
Hashtbl.replace seen x (old + 1))
lst;
let best = Hashtbl.fold (fun _ -> max) seen 0 in
Hashtbl.fold (fun k v acc ->
if v = best then k :: acc
else acc)
seen []</lang>
# mode [1;3;6;6;6;6;7;7;12;12;17];;
- : int list = [6]
# mode [1;1;2;4;4];;
- : int list = [4; 1]
Octave
Of course Octave has the mode function; but it returns only the "lowest" mode if multiple modes are available. <lang octave>function m = mode2(v)
sv = sort(v);
% build two vectors, vals and c, so that
% c(i) holds how many times vals(i) appears
i = 1; c = []; vals = [];
while (i <= numel(v) )
tc = sum(sv==sv(i)); % it would be faster to count
% them "by hand", since sv is sorted...
c = [c, tc];
vals = [vals, sv(i)];
i += tc;
endwhile
% stack vals and c building a 2-rows matrix x
x = cat(1,vals,c);
% sort the second row (frequencies) into t (most frequent
% first) and take the "original indices" i ...
[t, i] = sort(x(2,:), "descend");
% ... so that we can use them to sort columns according
% to frequencies
nv = x(1,i);
% at last, collect into m (the result) all the values
% having the same bigger frequency
r = t(1); i = 1;
m = [];
while ( t(i) == r )
m = [m, nv(i)];
i++;
endwhile
endfunction</lang> <lang octave>a = [1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]; mode2(a) mode(a)
a = [1, 1, 2, 4, 4]; mode2(a) % returns 1 and 4 mode(a) % returns 1 only</lang>
ooRexx
See the example at REXX, Version 2 for a version that returns multiple mode values. <lang ooRexx> -- will work with just about any collection... call testMode .array~of(10, 9, 8, 7, 6, 5, 4, 3, 2, 1) call testMode .list~of(10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0, .11) call testMode .queue~of(30, 10, 20, 30, 40, 50, -100, 4.7, -11e2)
- routine testMode
use arg list
say "list =" list~makearray~toString("l", ", ")
say "mode =" mode(list)
say
- routine mode
use arg list
-- this is a good application for a bag
-- add all of the items to the bag
collector = .bag~new
collector~putAll(list)
-- now get a list of unique items
indexes = .set~new~~putall(collector)
count = 0 -- this is used to keep track of the maximums
-- now see how many of each element we ended up with
loop index over indexes
items = collector~allat(index)
newCount = items~items
if newCount > count then do
mode = items[1]
count = newCount
end
end
return mode
</lang>
Oz
<lang oz>declare
fun {Mode Xs}
Freq = {Dictionary.new}
for X in Xs do
Freq.X := {CondSelect Freq X 0} + 1
end
MaxCount = {FoldL {Dictionary.items Freq} Max 0}
in
for Value#Count in {Dictionary.entries Freq} collect:C do
if Count == MaxCount then
{C Value}
end
end
end
in
{Show {Mode [1 2 3 3 2 1 1]}}
{Show {Mode [1 2 3 3 2 1]}}</lang>
PARI/GP
<lang parigp>mode(v)={
my(count=1,r=1,b=v[1]);
v=vecsort(v);
for(i=2,#v,
if(v[i]==v[i-1],
count++
,
if(count>r,
r=count;
b=v[i-1]
);
count=1
)
);
if(count>r,v[#v],b)
};</lang>
Perl
<lang perl>use strict; use List::Util qw(max);
sub mode {
my %c;
foreach my $e ( @_ ) {
$c{$e}++;
}
my $best = max(values %c);
return grep { $c{$_} == $best } keys %c;
}</lang>
<lang perl>print "$_ " foreach mode(1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17); print "\n"; print "$_ " foreach mode(1, 1, 2, 4, 4); print "\n";</lang>
Perl 6
<lang perl6>sub mode (*@a) {
my %counts;
++%counts{$_} for @a;
my $max = [max] values %counts;
return |map { .key }, grep { .value == $max }, %counts.pairs;
}</lang>
Phix
<lang Phix>function mode(sequence s) -- returns a list of the most common values, each of which occurs the same number of times object this integer nxt = 1, count = 1, maxc = 1 sequence res = {}
if length(s)!=0 then
s = sort(s)
this = s[1]
for i=2 to length(s) do
if s[i]!=this then
s[nxt] = {count,this}
nxt += 1
this = s[i]
count = 1
else
count += 1
if count>maxc then
maxc = count
end if
end if
end for
s[nxt] = {count,this}
res = ""
for i=1 to nxt do
if s[i][1]=maxc then
res = append(res,s[i][2])
end if
end for
end if
return res
end function
?mode({1, 2, 5, -5, -9.5, 3.14159}) ?mode({ 1, "blue", 2, 7.5, 5, "green", "red", 5, 2, "blue", "white" }) ?mode({1, 2, 3, 1, 2, 4, 2, 5, 2, 3, 3, 1, 3, 6}) ?mode({.2, .7, .1, .8, .2}) ?mode({"two", 7, 1, 8, "two", 8}) ?mode("Hello there world") ?mode({}) {} = wait_key()</lang>
- Output:
{-9.5,-5,1,2,3.14159,5}
{2,5,"blue"}
{2,3}
{0.2}
{8,"two"}
"el"
{}
PHP
Note: this function only works with strings and integers, as those are the only things that can be used as keys of an (associative) array in PHP. <lang php><?php function mode($arr) {
$count = array_count_values($arr); $best = max($count); return array_keys($count, $best);
}
print_r(mode(array(1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17))); print_r(mode(array(1, 1, 2, 4, 4))); ?></lang>
PicoLisp
<lang PicoLisp>(de modes (Lst)
(let A NIL
(for X Lst
(accu 'A X 1) )
(mapcar car
(maxi cdar
(by cdr group A) ) ) ) )</lang>
- Output:
: (modes (1 3 6 6 6 6 7 7 12 12 17))
-> (6)
: (modes (1 1 2 4 4))
-> (4 1)
: (modes (chop "ABRAHAMASANTACLARA"))
-> ("A")
: (modes (1 4 A 3 2 7 1 B B 3 6 2 4 C C 5 2 5 B A 3 2 C 3 5 5 4 C 7 7))
-> (5 C 2 3)
PL/I
<lang PL/I>av: procedure options (main); /* 28 October 2013 */
declare x(10) fixed binary static initial (1, 4, 2, 6, 2, 5, 6, 2, 4, 2); declare f(32767) fixed binary; declare (j, n, max, value) fixed binary; declare i fixed;
n = hbound(x,1);
do i = 1 to n;
j = x(i);
f(j) = f(j) + 1;
end;
max = 0;
do i = 1 to hbound(f,1);
if max < f(i) then do; max = f(i); value = i; end;
end;
put list ('The mode value is ' || value || ' occurred ' ||
max || ' times.');
end av;</lang> Results:
The mode value is 2 occurred 4 times.
PowerShell
<lang PowerShell>$data = @(1,1,1,2,3,4,5,5,6,7,7,7) $groups = $data | group-object | sort-object count -Descending $groups | ? {$_.Count -eq $groups[0].Count}</lang>
- Output:
Count Name Group
----- ---- -----
3 7 {7, 7, 7}
3 1 {1, 1, 1}
PureBasic
<lang PureBasic>Procedure mean(Array InArray(1))
Structure MyMean Value.i Cnt.i EndStructure
Protected i, max, found
Protected NewList MyDatas.MyMean()
Repeat
found=#False
ForEach MyDatas()
If InArray(i)=MyDatas()\Value
MyDatas()\Cnt+1
found=#True
Break
EndIf
Next
If Not found
AddElement(MyDatas())
MyDatas()\Value=InArray(i)
MyDatas()\cnt+1
EndIf
If MyDatas()\Cnt>max
max=MyDatas()\Cnt
EndIf
i+1
Until i>ArraySize(InArray())
ForEach MyDatas()
If MyDatas()\Cnt=max
For i=1 To max
Print(Str(MyDatas()\Value)+" ")
Next
EndIf
Next
EndProcedure</lang>
Python
The following solutions require that the elements be hashable.
<lang python>>>> from collections import defaultdict >>> def modes(values): count = defaultdict(int) for v in values: count[v] +=1 best = max(count.values()) return [k for k,v in count.items() if v == best]
>>> modes([1,3,6,6,6,6,7,7,12,12,17]) [6] >>> modes((1,1,2,4,4)) [1, 4]</lang>
<lang python>>>> from collections import Counter >>> def modes(values): count = Counter(values) best = max(count.values()) return [k for k,v in count.items() if v == best]
>>> modes([1,3,6,6,6,6,7,7,12,12,17]) [6] >>> modes((1,1,2,4,4)) [1, 4]</lang> If you just want one mode (instead of all of them), here's a one-liner for that: <lang python>def onemode(values):
return max(set(values), key=values.count)</lang>
R
<lang R>statmode <- function(v) {
a <- sort(table(v), decreasing=TRUE)
r <- c()
for(i in 1:length(a)) {
if ( a1 == ai ) {
r <- c(r, as.integer(names(a)[i]))
} else break; # since it's sorted, once we find
# a different value, we can stop
}
r
}
print(statmode(c(1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17))) print(statmode(c(1, 1, 2, 4, 4)))</lang>
Racket
Returns values of list of modes and their frequencies of appearance. <lang Racket>#lang racket
(define (mode seq)
(define frequencies (make-hash))
(for ([s seq])
(hash-update! frequencies
s
(lambda (freq) (add1 freq))
0))
(for/fold ([ms null]
[freq 0])
([(k v) (in-hash frequencies)])
(cond [(> v freq)
(values (list k) v)]
[(= v freq)
(values (cons k ms) freq)]
[else
(values ms freq)])))</lang>
REXX
version 1
Returns one mode value. <lang rexx>/*REXX program finds the mode (most occurring element) of a vector. */ /* ════════vector══════════─ ═══show vector═══ ═─═══show result═════ */
v= 1 8 6 0 1 9 4 6 1 9 9 9 ; say 'vector='v; say 'mode='mode(v); say
v= 1 2 3 4 5 6 7 8 9 11 10 ; say 'vector='v; say 'mode='mode(v); say
v= 8 8 8 2 2 2 ; say 'vector='v; say 'mode='mode(v); say
v='cat kat Cat emu emu Kat' ; say 'vector='v; say 'mode='mode(v); say
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ eSort: procedure expose @.; parse arg # 1 h /* [↓] this is an exchange sort. */
do while h>1; h=h%2 /*In REXX, % is an integer divide.*/
do i=1 for #-h; j=i; k=h+i /* [↓] perform exchange for elements. */
do while @.k<@.j & h<j; _=@.j; @.j=@.k; @.k=_; j=j-h; k=k-h; end
end /*i*/
end /*while h>1*/
return
/*──────────────────────────────────────────────────────────────────────────────────────*/ mode: procedure expose @.; parse arg x /*function finds the MODE of a vector*/
#=words(x) /*#: the number of elements in vector.*/
do k=1 for #; @.k=word(x,k); end /* ◄──── make an array from the vector.*/
call eSort # /*sort the elements in the array. */
?=@.1 /*assume the first element is the mode.*/
freq=1 /*the frequency of the occurrence. */
do j=1 for #; _=j-freq /*traipse through the elements in array*/
if @.j==@._ then do /*is this element the same as previous?*/
freq=freq+1 /*bump the frequency counter. */
?=@.j /*this element is the mode (···so far).*/
end
end /*j*/
return ? /*return the mode of vector to invoker.*/</lang>
output
vector=1 8 6 0 1 9 4 6 1 9 9 9 mode=9 vector=1 2 3 4 5 6 7 8 9 11 10 mode=1 vector=8 8 8 2 2 2 mode=2 vector=cat kat Cat emu emu Kat mode=emu
version 2
Displays all modes if there are more than one.
<lang REXX>/* Rexx */ /*-- ~~ main ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */ call run_samples return exit
/*-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */ /*-- returns a comma separated string of mode values from a comma separated input vector string */ mode:
procedure
parse arg lvector
drop vector.
vector. =
call makeStem lvector -- this call creates the "vector." stem from the input string
seen. = 0
modes. =
modeMax = 0
do v_ = 1 to vector.0
mv = vector.v_
seen.mv = seen.mv + 1
select
when seen.mv > modeMax then do
modeMax = seen.mv
drop modes.
modes. =
nx = 1
modes.0 = nx
modes.nx = mv
end
when seen.mv = modeMax then do
nx = modes.0 + 1
modes.0 = nx
modes.nx = mv
end
otherwise do
nop
end
end
end v_
lmodes = do e_ = 1 to modes.0 lmodes = lmodes modes.e_ end e_ lmodes = strip(space(lmodes, 1, ','))
return lmodes
/*-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */ /*-- pretty-print */ show_mode:
procedure parse arg lvector lmodes = mode(lvector) say 'Vector: ['space(lvector, 0)'], Mode(s): ['space(lmodes, 0)']' return modes
/*-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */ /*-- load the "vector." stem from the comma separated input vector string */ makeStem:
procedure expose vector. vector.0 = 0 parse arg lvector do v_ = 1 while lvector \= parse var lvector val ',' lvector vector.0 = v_ vector.v_ = strip(val) vector = strip(lvector) end v_ return vector.0
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ run_samples:
procedure call show_mode '10, 9, 8, 7, 6, 5, 4, 3, 2, 1' -- 10 9 8 7 6 5 4 3 2 1 call show_mode '10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0, 0.11' -- 0 call show_mode '30, 10, 20, 30, 40, 50, -100, 4.7, -11e+2' -- 30 call show_mode '30, 10, 20, 30, 40, 50, -100, 4.7, -11e+2, -11e+2' -- 30 -11e2 call show_mode '1, 8, 6, 0, 1, 9, 4, 6, 1, 9, 9, 9' -- 9 call show_mode '1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11' -- 1 2 3 4 5 6 7 8 9 10 11 call show_mode '8, 8, 8, 2, 2, 2' -- 8 2 call show_mode 'cat, kat, Cat, emu, emu, Kat' -- emu call show_mode '0, 1, 2, 3, 3, 3, 4, 4, 4, 4, 1, 0' -- 4 call show_mode '2, 7, 1, 8, 2' -- 2 call show_mode '2, 7, 1, 8, 2, 8' -- 8 2 call show_mode 'E, n, z, y, k, l, o, p, ä, d, i, e' -- E n z y k l o p ä d i e call show_mode 'E, n, z, y, k, l, o, p, ä, d, i, e, ä' -- ä call show_mode '3, 1, 4, 1, 5, 9, 7, 6' -- 1 call show_mode '3, 1, 4, 1, 5, 9, 7, 6, 3' -- 3, 1 call show_mode '1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17' -- 6 call show_mode '1, 1, 2, 4, 4' -- 4 1 return</lang>
- Output:
Vector: [10,9,8,7,6,5,4,3,2,1], Mode(s): [10,9,8,7,6,5,4,3,2,1] Vector: [10,9,8,7,6,5,4,3,2,1,0,0,0,0,0.11], Mode(s): [0] Vector: [30,10,20,30,40,50,-100,4.7,-11e+2], Mode(s): [30] Vector: [30,10,20,30,40,50,-100,4.7,-11e+2,-11e+2], Mode(s): [30,-11e+2] Vector: [1,8,6,0,1,9,4,6,1,9,9,9], Mode(s): [9] Vector: [1,2,3,4,5,6,7,8,9,10,11], Mode(s): [1,2,3,4,5,6,7,8,9,10,11] Vector: [8,8,8,2,2,2], Mode(s): [8,2] Vector: [cat,kat,Cat,emu,emu,Kat], Mode(s): [emu] Vector: [0,1,2,3,3,3,4,4,4,4,1,0], Mode(s): [4] Vector: [2,7,1,8,2], Mode(s): [2] Vector: [2,7,1,8,2,8], Mode(s): [2,8] Vector: [E,n,z,y,k,l,o,p,ä,d,i,e], Mode(s): [E,n,z,y,k,l,o,p,ä,d,i,e] Vector: [E,n,z,y,k,l,o,p,ä,d,i,e,ä], Mode(s): [ä] Vector: [3,1,4,1,5,9,7,6], Mode(s): [1] Vector: [3,1,4,1,5,9,7,6,3], Mode(s): [1,3] Vector: [1,3,6,6,6,6,7,7,12,12,17], Mode(s): [6] Vector: [1,1,2,4,4], Mode(s): [1,4]
Ruby
Here's two methods, the first more Ruby-ish, the second perhaps a bit more efficient. <lang ruby>def mode(ary)
seen = Hash.new(0)
ary.each {|value| seen[value] += 1}
max = seen.values.max
seen.find_all {|key,value| value == max}.map {|key,value| key}
end
def mode_one_pass(ary)
seen = Hash.new(0)
max = 0
max_elems = []
ary.each do |value|
seen[value] += 1
if seen[value] > max
max = seen[value]
max_elems = [value]
elsif seen[value] == max
max_elems << value
end
end
max_elems
end
p mode([1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]) # => [6] p mode([1, 1, 2, 4, 4]) # => [1, 4] p mode_one_pass([1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]) # => [6] p mode_one_pass([1, 1, 2, 4, 4]) # => [1, 4]</lang>
If you just want one mode (instead of all of them), here's a one-liner for that: <lang ruby>def one_mode(ary)
ary.max_by { |x| ary.count(x) }
end</lang>
Rust
<lang rust>use std::collections::HashMap;
fn main() {
let mode_vec1 = mode(vec![ 1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]); let mode_vec2 = mode(vec![ 1, 1, 2, 4, 4]);
println!("Mode of vec1 is: {:?}", mode_vec1);
println!("Mode of vec2 is: {:?}", mode_vec2);
assert!( mode_vec1 == [6], "Error in mode calculation"); assert!( (mode_vec2 == [1, 4]) || (mode_vec2 == [4,1]), "Error in mode calculation" );
}
fn mode(vs: Vec<i32>) -> Vec<i32> {
let mut vec_mode = Vec::new();
let mut seen_map = HashMap::new();
let mut max_val = 0;
for i in vs{
let ctr = seen_map.entry(i).or_insert(0);
*ctr += 1;
if *ctr > max_val{
max_val = *ctr;
}
}
for (key, val) in seen_map {
if val == max_val{
vec_mode.push(key);
}
}
vec_mode
} </lang>
- Output:
Mode of vec1 is: [6] Mode of vec2 is: [1,4] // may also print [4, 1], vector has no order guarantee
Scala
Receiving any collection is easy. Returning the result in the same collection takes some doing. <lang scala>import scala.collection.breakOut import scala.collection.generic.CanBuildFrom def mode
[T, CC[X] <: Seq[X]](coll: CC[T])
(implicit o: T => Ordered[T], cbf: CanBuildFrom[Nothing, T, CC[T]])
: CC[T] = {
val grouped = coll.groupBy(x => x).mapValues(_.size).toSeq
val max = grouped.map(_._2).max
grouped.filter(_._2 == max).map(_._1)(breakOut)
}</lang>
Scheme
<lang scheme>(define (mode collection)
(define (helper collection counts)
(if (null? collection)
counts
(helper (remove (car collection) collection)
(cons (cons (car collection)
(appearances (car collection) collection)) counts))))
(map car
(filter (lambda (x) (= (cdr x) (apply max (map cdr (helper collection '())))))
(helper collection '())))</lang>
Seed7
The example below defines the template function createModeFunction, which defines the function mode.
The template createModeFunction is instantiated explicit with createModeFunction(integer).
Additionally to mode the function str is defined.
The function str is used by the template function
enable_output to allow writing arrays.
This way the main function can just write the mode.
<lang seed7>$ include "seed7_05.s7i";
const proc: createModeFunction (in type: elemType) is func
begin
const func array elemType: mode (in array elemType: data) is func
result
var array elemType: maxElems is 0 times elemType.value;
local
var hash [elemType] integer: counts is (hash [elemType] integer).value;
var elemType: aValue is elemType.value;
var integer: maximum is 0;
begin
for aValue range data do
if aValue in counts then
incr(counts[aValue]);
else
counts @:= [aValue] 1;
end if;
if counts[aValue] > maximum then
maximum := counts[aValue];
maxElems := [] (aValue);
elsif counts[aValue] = maximum then
maxElems &:= aValue;
end if;
end for;
end func;
const func string: str (in array elemType: data) is func
result
var string: result is "";
local
var elemType: anElement is elemType.value;
begin
for anElement range data do
result &:= " " & str(anElement);
end for;
result := result[2 ..];
end func;
enable_output(array elemType);
end func;
createModeFunction(integer);
const proc: main is func
begin writeln(mode([] (1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17))); writeln(mode([] (1, 1, 2, 4, 4))); end func;</lang>
- Output:
6 1 4
Sidef
<lang ruby>func mode(array) {
var c = Hash.new;
array.each{|i| c{i} := 0 ++};
var max = c.values.max;
c.keys.grep{|i| c{i} == max};
}</lang>
Calling the function <lang ruby>say mode([1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17]).join(' '); say mode([1, 1, 2, 4, 4]).join(' ');</lang>
- Output:
6 1 4
If you just want one mode (instead of all of them), here's a one-liner for that:
<lang ruby>func one_mode(arr) {
arr.max_by{|i| arr.count(i)};
}</lang>
Slate
<lang Slate>s@(Sequence traits) mode [| sortedCounts |
sortedCounts: (s as: Bag) sortedCounts. (sortedCounts mapSelect: [| :count :elem | sortedCounts last count = count]) valueSet
].</lang>
Smalltalk
This code is able to find the mode of any collection of any kind of object. <lang smalltalk>OrderedCollection extend [
mode [ |s|
s := self asBag sortedByCount.
^ (s select: [ :k | ((s at: 1) key) = (k key) ]) collect: [:k| k value]
]
].
- ( 1 3 6 6 6 6 7 7 12 12 17 ) asOrderedCollection
mode displayNl.
- ( 1 1 2 4 4) asOrderedCollection
mode displayNl.</lang>
Tcl
<lang tcl># Can find the modal value of any vector of values proc mode {n args} {
foreach n [list $n {*}$args] {
dict incr counter $n
}
set counts [lsort -stride 2 -index 1 -decreasing $counter]
set best {}
foreach {n count} $counts {
if {[lindex $counts 1] == $count} {
lappend best $n
} else break
}
return $best
}
- Testing
puts [mode 1 3 6 6 6 6 7 7 12 12 17]; # --> 6 puts [mode 1 1 2 4 4]; # --> 1 4</lang> Note that this works for any kind of value.
UNIX Shell
<lang bash>#!/bin/bash
function mode {
declare -A map max=0 for x in "$@"; do
tmp=$((${map[$x]} + 1)) map[$x]=$tmp ((tmp > max)) && max=$tmp
done
for x in "${!map[@]}"; do
[[ ${map[$x]} == $max ]] && echo -n "$x "
done echo
}</lang> <lang bash>mode 1 2 1 2 a b a b a 2 a 2</lang>
Ursala
The mode function defined below works on lists of any type and returns a list of the modes. There is no concept of a general collection in Ursala. The algorithm is to partition the list by equality, then partition the classes by their lengths, and then select a representative from each member of the set of classes with the maximum length. <lang Ursala>#import std
mode = ~&hS+ leql$^&h+ eql|=@K2
- cast %nLW
examples = mode~~ (<1,3,6,6,6,7,7,12,12,17>,<1,1,2,4,4>)</lang> The function is tested on a pair of lists, one with a unique mode and one with multiple modes.
- Output:
(<6>,<4,1>)
Vedit macro language
Current edit buffer stores the collection. Each line is an item in the collection. The items can be any type (ascii text, numeric values in ascii, binary values). However, binary file with fixed record length would require some modifications to the code.
The "mode" item and it's count are displayed on status line. If there are multiple items with the same count, the smallest one is displayed. <lang vedit>BOF // Copy all data to a new buffer Reg_Copy(10, ALL) Buf_Switch(Buf_Free) Reg_Ins(10)
Sort(0, File_Size) // Sort the data
BOF repeat(ALL) { // Count & delete duplicate lines
#1 = 1
while(Match("^{.*}\N\1$", REGEXP)==0) {
Del_Line(1)
#1++
}
Num_Ins(#1, NOCR) // Insert item count at the beginning of line
Ins_Char(9) // TAB
Line(1, ERRBREAK) // Next (different) line
}
Sort(0, File_Size, REVERSE) // Sort according to the count
BOF // Display the results Reg_Copy_Block(10, CP, EOL_pos) Buf_Quit(OK) Statline_Message(@10)</lang>
Wren
<lang wren>class Arithmetic {
static mode(arr) {
var map = {}
for (e in arr) {
if (map[e] == null) map[e] = 0
map[e] = map[e] + 1
}
var max = map.values.reduce {|x, y| x > y ? x : y}
return map.keys.where {|x| map[x] == max}.toList
}
}
System.print(Arithmetic.mode([1,2,3,4,5,5,51,2,3])) </lang>
- Output:
[2, 3, 5]
Order may differ
XEmacs Lisp
This returns a list of the modes. Any type(s) of data can be passed in, and any "equal" predicate function can be specified. <lang xelisp>(defun mode ( predicate &rest values)
"Finds the mode of all values passed in.
Uses `predicate' to compare items."
(let ((modes nil) ; Declare local variables
(mode-count 0) (value-list nil) current-value)
(loop for value in values do
(if (setq current-value (assoc* value value-list :test predicate)) ; Construct a linked list of cons cells, (value . count)
(incf (cdr current-value)) (push (cons value 1) value-list)))
(loop for (value . count) in value-list do ; Find modes in linked list
(if (> count mode-count)
(setq modes (list value) mode-count count) (when (eq count mode-count) (push value modes))))
modes))</lang>
zkl
This is a bit funky in that modes are returned as strings.
<lang zkl>fcn mode(items){
d:=D(); foreach i in (items){ d[i]=d.find(i,0)+1 }
m:=d.reduce(fcn(m,[(_,v)]){ v.max(m) },0);
// d.keys.filter('wrap(k){ d[k]==m }); // more garbage than necessary
d.filter('wrap([(_,v)]){ v==m }).apply("get",0);
}</lang> <lang zkl>data:=T(1, 2, 3, 1, 2, 4, 2, 5, 3, 3, 1, 3, 6); println("Mode: ", mode(data)); println("Mode: ", mode(data.append(2))); println("Mode: ", mode("this is a test".split("")));</lang>
- Output:
Mode: L("3")
Mode: L("2","3")
Mode: L("s","t"," ")
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