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Entropy: Difference between revisions
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{{out}}
<pre>1.8464393</pre>
==={{header|uBasic/4tH}}===
{{Trans|QBasic}}
uBasic/4tH is an integer BASIC only. So, fixed point arithmetic is required go fulfill this task. Some loss of precision is unavoidable.
<syntaxhighlight lang="basic">If Info("wordsize") < 64 Then Print "This program requires a 64-bit uBasic" : End
s := "1223334444"
u := ""
x := FUNC(_Fln(FUNC(_Ntof(2)))) ' calculate LN(2)
For i = 0 TO Len(s)-1
k = 0
For j = 0 TO Len(u)-1
If Peek(u, j) = Peek(s, i) Then k = 1
Next
If k = 0 THEN u = Join(u, Char (Peek (s, i)))
Next
Dim @r(Len(u)-1)
For i = 0 TO Len(u)-1
c = 0
For J = 0 TO Len(s)-1
If Peek(u, i) = Peek (s, j) Then c = c + 1
Next
q = FUNC(_Fdiv(c, Len(s)))
@r(i) = FUNC(_Fmul(q, FUNC(_Fdiv(FUNC(_Fln(q)), x))))
Next
e = 0
For i = 0 To Len(u) - 1
e = e - @r(i)
Next
Print Using "+?.####"; FUNC(_Ftoi(e))
End
_Fln Param (1) : Return (FUNC(_Ln(a@*4))/4)
_Fmul Param (2) : Return ((a@*b@)/16384)
_Fdiv Param (2) : Return ((a@*16384)/b@)
_Ntof Param (1) : Return (a@*16384)
_Ftoi Param (1) : Return ((10000*a@)/16384)
_Ln
Param (1)
Local (2)
c@=681391
If (a@<32768) Then a@=SHL(a@, 16) : c@=c@-726817
If (a@<8388608) Then a@=SHL(a@, 8) : c@=c@-363409
If (a@<134217728) Then a@=SHL(a@, 4) : c@=c@-181704
If (a@<536870912) Then a@=SHL(a@, 2) : c@=c@-90852
If (a@<1073741824) Then a@=SHL(a@, 1) : c@=c@-45426
b@=a@+SHL(a@, -1) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-26573
b@=a@+SHL(a@, -2) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-14624
b@=a@+SHL(a@, -3) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-7719
b@=a@+SHL(a@, -4) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-3973
b@=a@+SHL(a@, -5) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-2017
b@=a@+SHL(a@, -6) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-1016
b@=a@+SHL(a@, -7) : If (AND(b@, 2147483648)) = 0 Then a@=b@ : c@=c@-510
a@=2147483648-a@;
c@=c@-SHL(a@, -15)
Return (c@)</syntaxhighlight>
{{Out}}
<pre>1.8461
0 OK, 0:638</pre>
=={{header|BBC BASIC}}==
Line 815 ⟶ 882:
readln;
end.</syntaxhighlight>
=={{header|EasyLang}}==
<syntaxhighlight>
func entropy s$ .
len d[] 255
for c$ in strchars s$
d[strcode c$] += 1
.
for cnt in d[]
if cnt > 0
prop = cnt / len s$
entr -= (prop * log10 prop / log10 2)
.
.
return entr
.
print entropy "1223334444"
</syntaxhighlight>
=={{header|EchoLisp}}==
Line 856 ⟶ 941:
=={{header|Elena}}==
{{trans|C#}}
ELENA
<syntaxhighlight lang="elena">import system'math;
import system'collections;
Line 874 ⟶ 959:
var table := Dictionary.new();
input.forEach::(ch)
{
var n := table[ch];
Line 888 ⟶ 973:
var freq := 0;
table.forEach::(letter)
{
freq := letter.toInt().realDiv(input.Length);
Line 990 ⟶ 1,075:
>entropy("1223334444")
1.84643934467</syntaxhighlight>
=={{header|Excel}}==
This solution uses the <code>LAMBDA</code>, <code>LET</code>, and <code>MAP</code> functions introduced into the Microsoft 365 version of Excel in 2021. The <code>LET</code> function is able to use functions as first class citizens. Taking advantage of this makes the solution much simpler. The solution below looks for the string in cell <code>A1</code>.
<syntaxhighlight lang="excel">
=LET(
_MainS,A1,
_N,LEN(_MainS),
_Chars,UNIQUE(MID(_MainS,SEQUENCE(LEN(_MainS),1,1,1),1)),
calcH,LAMBDA(_c,(_c/_N)*LOG(_c/_N,2)),
getCount,LAMBDA(_i,LEN(_MainS)-LEN(SUBSTITUTE(_MainS,_i,""))),
_CharMap,MAP(_Chars,LAMBDA(a, calcH(getCount(a)))),
-SUM(_CharMap)
)
</syntaxhighlight>
_Chars uses the <code>SEQUENCE</code> function to split the text into an array. The <code>UNIQUE</code> function then returns a list of unique characters in the string.
<code>calcH</code> applies the calculation described at the top of the page that will then be summed for each character
<code>getCount</code> uses the <code>SUBSTITUTE</code> method to count the occurrences of a character within the string.
If you needed to re-use this calculation then you could wrap it in a <code>LAMBDA</code> function within the name manager, changing <code>A1</code> to a variable name (e.g. <code>String</code>):
<syntaxhighlight lang="excel">
ShannonEntropyH2=LAMBDA(String,LET(_MainS,String,_N,LEN(_MainS),_Chars,UNIQUE(MID(_MainS,SEQUENCE(LEN(_MainS),1,1,1),1)),calcH,LAMBDA(_c,(_c/_N)*LOG(_c/_N,2)),getCount,LAMBDA(_i,LEN(_MainS)-LEN(SUBSTITUTE(_MainS,_i,""))),_CharMap,MAP(_Chars,LAMBDA(a, calcH(getCount(a)))),-SUM(_CharMap)))
</syntaxhighlight>
Then you can just use the named lambda. E.g. If A1 = 1223334444 then:
<syntaxhighlight lang="excel">
=ShannonEntropyH2(A1)
</syntaxhighlight>
Returns 1.846439345
=={{header|F_Sharp|F#}}==
Line 1,185 ⟶ 1,301:
{{FormulaeEntry|page=https://formulae.org/?script=examples/Entropy}}
'''Solution'''
[[File:Fōrmulæ - Entropy 01.png]]
'''Test case'''
[[File:Fōrmulæ - Entropy 02.png]]
[[File:Fōrmulæ - Entropy 03.png]]
[[File:Fōrmulæ - Entropy 04.png]]
[[File:Fōrmulæ - Entropy 05.png]]
=={{header|Go}}==
Line 1,528 ⟶ 1,658:
<pre>entropy("1223334444") = 1.8464393446710154
entropy([1, 2, 3, 1, 2, 1, 2, 3, 1, 2, 3, 4, 5]) = 2.103909910282364</pre>
=={{header|K}}==
{{works with|ngn/k}}
<syntaxhighlight lang="k">entropy: {(`ln[#x]-(+/{x*`ln@x}@+/{x=\:?x}x)%#x)%`ln@2}
entropy "1223334444"</syntaxhighlight>
{{out}}
<pre>1.8464393446710161</pre>
=={{header|Kotlin}}==
<syntaxhighlight lang="
fun log2(d: Double) = Math.log(d) / Math.log(2.0)
Line 1,563 ⟶ 1,701:
for (sample in samples) println("${sample.padEnd(36)} -> ${"%18.16f".format(shannon(sample))}")
}</syntaxhighlight>
{{out}}
<pre>
Line 2,922 ⟶ 3,059:
'''NEXT'''
NEG SWAP DROP
≫ ≫ '<span style="color:blue">NTROP</span>' STO
|
<span style="color:blue">NTROP</span> ''( "string" -- entropy )''
Initialize local variables
Initialize a vector with 255 counters
Line 2,938 ⟶ 3,075:
|}
The following line of code
"1223334444" <span style="color:blue">NTROP</span>
{{out}}
<pre>
Line 3,151 ⟶ 3,288:
1.84644
</pre>
=={{header|SETL}}==
<syntaxhighlight lang="setl">program shannon_entropy;
print(entropy "1223334444");
op entropy(symbols);
hist := {};
loop for symbol in symbols do
hist(symbol) +:= 1;
end loop;
h := 0.0;
loop for count = hist(symbol) do
f := count / #symbols;
h -:= f * log f / log 2;
end loop;
return h;
end op;
end program; </syntaxhighlight>
{{out}}
<pre>1.84643934467102</pre>
=={{header|Sidef}}==
Line 3,260 ⟶ 3,417:
=={{header|Wren}}==
{{trans|Go}}
<syntaxhighlight lang="
var m = {}
for (c in s) {
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