Write float arrays to a text file

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Task
Write float arrays to a text file
You are encouraged to solve this task according to the task description, using any language you may know.

Write two equal-sized numerical arrays 'x' and 'y' to a two-column text file named 'filename'.

The first column of the file contains values from an 'x'-array with a given 'xprecision', the second -- values from 'y'-array with 'yprecision'.

For example, considering:

   x = {1, 2, 3, 1e11};
   y = {1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791}; 
                                                          /* sqrt(x) */
   xprecision = 3;
   yprecision = 5;

The file is:

   1    1
   2    1.4142
   3    1.7321
   1e+011   3.1623e+005

This task is intended as a subtask for Measure relative performance of sorting algorithms implementations.

Contents

[edit] Ada

with Ada.Text_IO;                       use Ada.Text_IO;
with Ada.Float_Text_IO; use Ada.Float_Text_IO;
with Ada.Numerics.Elementary_Functions; use Ada.Numerics.Elementary_Functions;
 
procedure Write_Float_Array is
type Float_Array is array (1..4) of Float;
procedure Write_Columns
( File  : File_Type;
X  : Float_Array;
Y  : Float_Array;
X_Pres : Natural := 3;
Y_Pres : Natural := 5
) is
begin
for I in Float_Array'range loop
Put (File => File, Item => X(I), Fore => 1, Aft => X_Pres - 1);
Put (File, " ");
Put (File => File, Item => Y(I), Fore => 1, Aft => Y_Pres - 1);
New_Line (File);
end loop;
end Write_Columns;
 
File : File_Type;
X : Float_Array := (1.0, 2.0, 3.0, 1.0e11);
Y : Float_Array;
begin
Put ("Tell us the file name to write:");
Create (File, Out_File, Get_Line);
for I in Float_Array'range loop
Y(I) := Sqrt (X (I));
end loop;
Write_columns (File, X, Y);
Close (File);
end Write_Float_Array;

[edit] ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
PROC writedat = (STRING filename, []REAL x, y, INT x width, y width)VOID: (
FILE f;
INT errno = open(f, filename, stand out channel);
IF errno NE 0 THEN stop FI;
FOR i TO UPB x DO
# FORMAT := IF the absolute exponent is small enough, THEN use fixed ELSE use float FI; #
FORMAT repr x := ( ABS log(x[i])<x width | $g(-x width,x width-2)$ | $g(-x width,x width-4,-1)$ ),
repr y := ( ABS log(y[i])<y width | $g(-y width,y width-2)$ | $g(-y width,y width-4,-1)$ );
putf(f, (repr x, x[i], $" "$, repr y, y[i], $l$))
OD;
close(f)
);
# Example usage: #
test:(
[]REAL x = (1, 2, 3, 1e11);
[UPB x]REAL y; FOR i TO UPB x DO y[i]:=sqrt(x[i]) OD;
printf(($"x before:"$, $xg$, x, $l$));
printf(($"y before:"$, $xg$, y, $l$));
writedat("sqrt.dat", x, y, 3+2, 5+2);
 
printf($"After:"l$);
FILE sqrt dat;
INT errno = open(sqrt dat, "sqrt.dat", stand in channel);
IF errno NE 0 THEN stop FI;
on logical file end(sqrt dat, (REF FILE sqrt dat)BOOL: stop);
TO UPB x DO
STRING line;
get(sqrt dat, (line, new line));
print((line,new line))
OD
)
Output:
x before: +1.00000000000000e  +0 +2.00000000000000e  +0 +3.00000000000000e  +0 +1.00000000000000e +11
y before: +1.00000000000000e  +0 +1.41421356237310e  +0 +1.73205080756888e  +0 +3.16227766016838e  +5
After:
1.000 1.00000
2.000 1.41421
3.000 1.73205
 1e11  316228

[edit] AWK

As usual, the order of array traversal in AWK is not necessarily the same as the input had:

$ awk 'BEGIN{split("1 2 3 1e11",x);
> split("1 1.4142135623730951 1.7320508075688772 316227.76601683791",y);
> for(i in x)printf("%6g %.5g\n",x[i],y[i])}'
1e+11 3.1623e+05
1 1
2 1.4142
3 1.7321

For the text file part of the task, just redirect stdout to it.

[edit] BBC BASIC

      DIM x(3), y(3)
x() = 1, 2, 3, 1E11
FOR i% = 0 TO 3
y(i%) = SQR(x(i%))
NEXT
 
xprecision = 3
yprecision = 5
 
outfile% = OPENOUT("filename.txt")
IF outfile%=0 ERROR 100, "Could not create file"
 
FOR i% = 0 TO 3
@% = &1000000 + (xprecision << 8)
a$ = STR$(x(i%)) + CHR$(9)
@% = &1000000 + (yprecision << 8)
a$ += STR$(y(i%))
PRINT #outfile%, a$ : BPUT #outfile%, 10
NEXT
 
CLOSE #outfile%
Output:
1	1
2	1.4142
3	1.7321
1E11	3.1623E5

[edit] C

#include <stdio.h>
#include <math.h>
 
int main(int argc, char **argv) {
 
float x[4] = {1,2,3,1e11}, y[4];
int i = 0;
FILE *filePtr;
 
filePtr = fopen("floatArray","w");
 
for (i = 0; i < 4; i++) {
y[i] = sqrt(x[i]);
fprintf(filePtr, "%.3g\t%.5g\n", x[i], y[i]);
}
 
return 0;
}

The file "floatArray" then contains the following:

1       1
2 1.4142
3 1.7321
1e+11 3.1623e+05

[edit] C++

Function writedat():

template<class InputIterator, class InputIterator2>
void writedat(const char* filename,
InputIterator xbegin, InputIterator xend,
InputIterator2 ybegin, InputIterator2 yend,
int xprecision=3, int yprecision=5)
{
std::ofstream f;
f.exceptions(std::ofstream::failbit | std::ofstream::badbit);
f.open(filename);
for ( ; xbegin != xend and ybegin != yend; ++xbegin, ++ybegin)
f << std::setprecision(xprecision) << *xbegin << '\t'
<< std::setprecision(yprecision) << *ybegin << '\n';
}

Example:

#include <algorithm>
#include <cmath> // ::sqrt()
#include <fstream>
#include <iomanip> // setprecision()
#include <iostream>
#include <string>
#include <vector>
 
int main()
{
try {
// prepare test data
double x[] = {1, 2, 3, 1e11};
const size_t xsize = sizeof(x) / sizeof(*x);
std::vector<double> y(xsize);
std::transform(&x[0], &x[xsize], y.begin(), ::sqrt);
 
// write file using default precisions
writedat("sqrt.dat", &x[0], &x[xsize], y.begin(), y.end());
 
// print the result file
std::ifstream f("sqrt.dat");
for (std::string line; std::getline(f, line); )
std::cout << line << std::endl;
}
catch(std::exception& e) {
std::cerr << "writedat: exception: '" << e.what() << "'\n";
return 1;
}
return 0;
}
Result:
1       1
2       1.4142
3       1.7321
1e+11   3.1623e+05

[edit] Common Lisp

(with-open-file (stream (make-pathname :name "filename") :direction :output)
(let* ((x (make-array 4 :initial-contents '(1 2 3 1e11)))
(y (map 'vector 'sqrt x))
(xprecision 3)
(yprecision 5)
(fmt (format nil "~~,1,~d,,G~~12t~~,~dG~~%" xprecision yprecision)))
(map nil (lambda (a b)
(format stream fmt a b)) x y)))

Using CLISP I get

1.          1.0000
2.          1.4142
3.          1.7321
1.0E+011    3.16228E+5

[edit] D

import std.file, std.conv, std.string;
 
void main() {
auto x = [1.0, 2, 3, 1e11];
auto y = [1.0, 1.4142135623730951,
1.7320508075688772, 316227.76601683791];
int xPrecision = 3,
yPrecision = 5;
 
string tmp;
foreach (i, fx; x)
tmp ~= format("%." ~ text(xPrecision) ~ "g  %." ~
text(yPrecision) ~ "g\r\n", fx, y[i]);
 
write("float_array.txt", tmp);
}
Output:
1	1
2	1.4142
3	1.7321
1e+11	3.1623e+05

[edit] Erlang

Erlang thinks 1 is an integer. To persuade it otherwise I have to use 1.0.

 
-module( write_float_arrays ).
 
-export( [task/0, to_a_text_file/3, to_a_text_file/4] ).
 
task() ->
File = "afile",
Xs = [1.0, 2.0, 3.0, 1.0e11],
Ys = [1.0, 1.4142135623730951, 1.7320508075688772, 316227.76601683791],
Options = [{xprecision, 3}, {yprecision, 5}],
to_a_text_file( File, Xs, Ys, Options ),
{ok, Contents} = file:read_file( File ),
io:fwrite( "File contents: ~p~n", [Contents] ).
 
to_a_text_file( File, Xs, Ys ) -> to_a_text_file( File, Xs, Ys, [] ).
 
to_a_text_file( File, Xs, Ys, Options ) ->
Xprecision = proplists:get_value( xprecision, Options, 2 ),
Yprecision = proplists:get_value( yprecision, Options, 2 ),
Format = lists:flatten( io_lib:format("~~.~pg ~~.~pg~n", [Xprecision, Yprecision]) ),
{ok, IO} = file:open( File, [write] ),
[ok = io:fwrite( IO, Format, [X, Y]) || {X, Y} <- lists:zip( Xs, Ys)],
file:close( IO ).
 
Output:
3> write_float_arrays:task().
File contents: <<"1.00 1.0000\n2.00 1.4142\n3.00 1.7321\n1.00e+11 3.1623e+5\n">>

[edit] Euphoria

constant x = {1, 2, 3, 1e11},
y = {1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791}
 
integer fn
 
fn = open("filename","w")
for n = 1 to length(x) do
printf(fn,"%.3g\t%.5g\n",{x[n],y[n]})
end for
close(fn)


[edit] F#

[<EntryPoint>]
let main argv =
let x = [ 1.; 2.; 3.; 1e11 ]
let y = List.map System.Math.Sqrt x
 
let xprecision = 3
let yprecision = 5
 
use file = System.IO.File.CreateText("float.dat")
let line = sprintf "%.*g\t%.*g"
List.iter2 (fun x y -> file.WriteLine (line xprecision x yprecision y)) x y
0

Content of File, visualized with TAB=8

1       1
2       1.4142
3       1.7321
1e+11   3.1623e+05

[edit] Forth

Works with: GNU Forth
create x  1e f, 2e       f, 3e       f, 1e11       f,
create y 1e f, 2e fsqrt f, 3e fsqrt f, 1e11 fsqrt f,
 
: main
s" sqrt.txt" w/o open-file throw to outfile-id
 
4 0 do
4 set-precision
x i floats + f@ f.
6 set-precision
y i floats + f@ f. cr
loop
 
outfile-id stdout to outfile-id
close-file throw ;

[edit] Fortran

In ANSI FORTRAN 77 or later use OPEN STATEMENT, and formatted WRITE statement with implied DO loop:

   real x(4), y(4)
data x / 1.0, 2.0, 4.0, 1.0e11 /
 
do 10 i = 1, 4
y = sqrt(x)
10 continue
 
open(unit=15, file='two_cols.txt', status='new')
write(15,'(f20.3,f21.4)') (x(I), y(I), I = 1, 4)
end
Works with: Fortran version 90 and later
program writefloats
implicit none
 
real, dimension(10) :: a, sqrta
integer :: i
integer, parameter :: unit = 40
 
a = (/ (i, i=1,10) /)
sqrta = sqrt(a)
 
open(unit, file="xydata.txt", status="new", action="write")
call writexy(unit, a, sqrta)
close(unit)
 
contains
 
subroutine writexy(u, x, y)
real, dimension(:), intent(in) :: x, y
integer, intent(in) :: u
 
integer :: i
 
write(u, "(2F10.4)") (x(i), y(i), i=lbound(x,1), ubound(x,1))
end subroutine writexy
 
end program writefloats

The arrays x and y should have same bounds (and size); this constraint is not checked.

[edit] Go

package main
 
import (
"fmt"
"os"
)
 
var (
x = []float64{1, 2, 3, 1e11}
y = []float64{1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791}
 
xprecision = 3
yprecision = 5
)
 
func main() {
if len(x) != len(y) {
fmt.Println("x, y different length")
return
}
f, err := os.Create("filename")
if err != nil {
fmt.Println(err)
return
}
for i := range x {
fmt.Fprintf(f, "%.*e, %.*e\n", xprecision-1, x[i], yprecision-1, y[i])
}
f.Close()
}

File contents:

1.00e+00, 1.0000e+00
2.00e+00, 1.4142e+00
3.00e+00, 1.7321e+00
1.00e+11, 3.1623e+05

[edit] Haskell

Probably not very idiomatic but oh well

import System.IO
import Text.Printf
import Control.Monad
 
writeDat filename x y xprec yprec =
withFile filename WriteMode $ \h ->
-- Haskell's printf doesn't support a precision given as an argument for some reason, so we insert it into the format manually:
let writeLine = hPrintf h $ "%." ++ show xprec ++ "g\t%." ++ show yprec ++ "g\n" in
zipWithM_ writeLine x y

Example usage

Prelude> let x = [1, 2, 3, 1e11]
Prelude> let y = map sqrt x
Prelude> y
[1.0,1.4142135623730951,1.7320508075688772,316227.7660168379]
Prelude> writeDat "sqrt.dat" x y 3 5
Prelude> readFile "sqrt.dat" >>= putStr
1.000	1.00000
2.000	1.41421
3.000	1.73205
1.000e11	316227.76602

Alternative solution without Printf

import System.IO
import Control.Monad
import Numeric
 
writeDat filename x y xprec yprec =
withFile filename WriteMode $ \h ->
let writeLine a b = hPutStrLn h $ showGFloat (Just xprec) a "" ++ "\t" ++ showGFloat (Just yprec) b "" in
zipWithM_ writeLine x y

[edit] HicEst

REAL :: n=4, x(n), y(n)
CHARACTER :: outP = "Test.txt"
 
OPEN(FIle = outP)
x = (1, 2, 3, 1E11)
y = x ^ 0.5
DO i = 1, n
WRITE(FIle=outP, Format='F5, F10.3') x(i), y(i)
ENDDO

Alternative: Display or Edit the formatted arrays in a spreadsheet-like dialog with a common scroll bar. The menu More - Export - File writes the formatted arrays to a file:

DLG(Text=x, Format='i12', Edit=y, Format='F10.2', Y=0)

[edit] Icon and Unicon

The following works in both languages.

link printf
 
procedure main()
every put(x := [], (1 to 3) | 1e11)
every put(y := [], sqrt(!x))
every fprintf(open("filename","w"),"%10.2e %10.4e\n", x[i := 1 to *x], y[i])
end

Contents of filename after running:

->cat filename
    1.00e0   1.0000e0
    2.00e0   1.4142e0
    3.00e0   1.7321e0
  1.00e+11  3.1623e+5
->

[edit] IDL

; the data:
x = [1,2,3,1e11]
y=sqrt(x)
xprecision=3
yprecision=5
 
; NOT how one would do things in IDL, but in the spirit of the task - the output format:
form = string(xprecision,yprecision,format='("(G0.",I0.0,",1x,G0.",I0.0,")")')
 
; file I/O:
openw,unit,"datafile.txt",/get
  for i = 1L, n_elements(x) do printf, unit, x[i-1],y[i-1],format=form
free_lun,unit

The file "datafile.txt" then contains the following:

1 1
2 1.4142
3 1.7321
1E+011 3.1623E+005

This is fairly ugly and un-IDLish. For example one shouldn't just rely on x and y having the same size. And if data is output in human-readable form, it should probably be lined up more nicely. And if it really has to be in two-column format with x and y side by side, one might consider running ASCII_Template or some such instead of that ugly hand-formatting.

[edit] J

require 'files'            NB.  for fwrites
 
x =. 1 2 3 1e11
y =.  %: x NB. y is sqrt(x)
 
xprecision =. 3
yprecision =. 5
 
filename =. 'whatever.txt'
 
data =. (0 j. xprecision,yprecision) ": x,.y
 
data fwrites filename

Or, more concisely:

((0 j. 3 5) ": (,.%:) 1 2 3 1e11) fwrites 'whatever.txt' [ require 'fwrites'

This loses all of the inline comments and names, and instead relies on the reader's understanding of the purpose of each of the names (for example: 3 is the precision of the first column, and 5 is the precision of the second column).

Note that J's idea of precision here is "positions after the decimal point":

   (0 j. 3 5) ": (,.%:) 1 2 3 1e11
1.000 1.00000
2.000 1.41421
3.000 1.73205
100000000000.000 316227.76602

[edit] Java

import java.io.*;
 
public class FloatArray {
public static void writeDat(String filename, double[] x, double[] y,
int xprecision, int yprecision)
throws IOException {
assert x.length == y.length;
PrintWriter out = new PrintWriter(filename);
for (int i = 0; i < x.length; i++)
out.printf("%."+xprecision+"g\t%."+yprecision+"g\n", x[i], y[i]);
out.close();
}
 
public static void main(String[] args) {
double[] x = {1, 2, 3, 1e11};
double[] y = new double[x.length];
for (int i = 0; i < x.length; i++)
y[i] = Math.sqrt(x[i]);
 
try {
writeDat("sqrt.dat", x, y, 3, 5);
} catch (IOException e) {
System.err.println("writeDat: exception: "+e);
}
 
try {
BufferedReader br = new BufferedReader(new FileReader("sqrt.dat"));
String line;
while ((line = br.readLine()) != null)
System.out.println(line);
} catch (IOException e) { }
}
}

[edit] Joy

 
DEFINE write-floats ==
['g 0] [formatf] enconcat map rollup
['g 0] [formatf] enconcat map swap zip
"filename" "w" fopen swap
[[fputchars] 9 fputch] step 10 fputch] step
fclose.
 

Using it:

[1.0 2.0 3.0 1e11] 3
[1.0 1.41421356 1.73205080 316227.7660168] 5
write-floats.

[edit] Julia

xprecision = 3
yprecision = 5
x = round([1, 2, 3, 1e11],xprecision)
y = round([1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791],yprecision)
writedlm("filename", [x y], '\t')

[edit] Lua

filename = "file.txt"
 
x = { 1, 2, 3, 1e11 }
y = { 1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791 };
xprecision = 3;
yprecision = 5;
 
fstr = "%."..tostring(xprecision).."f ".."%."..tostring(yprecision).."f\n"
 
fp = io.open( filename, "w+" )
 
for i = 1, #x do
fp:write( string.format( fstr, x[i], y[i] ) )
end
 
io.close( fp )


[edit] Mathematica

exportPrec[path_, data1_, data2_, prec1_, prec2_]:=Export[path,Transpose[{Map[ToString[NumberForm[#, prec2]] &, data2],Map[ToString[NumberForm[#, prec1]] &, data1]}], "Table"]

[edit] MATLAB / Octave

    x = [1, 2, 3, 1e11];
y = [1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791];
 
fid = fopen('filename','w')
fprintf(fid,'%.3g\t%.5g\n',[x;y]);
fclose(fid);
Output:
1	1
2	1.4142
3	1.7321
1e+11	3.1623e+05


[edit] NetRexx

/* NetRexx */
 
options replace format comments java crossref savelog symbols nobinary
 
-- Invent a target text file name based on this program's source file name
parse source . . pgmName '.nrx' .
outFile = pgmName || '.txt'
 
do
formatArrays(outFile, [1, 2, 3, 1e+11], [1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791])
catch ex = Exception
ex.printStackTrace
end
 
return
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- This function formats the input arrays.
-- It has defaults for the x & y precision values of 3 & 5
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method formatArrays(outFile, xf = Rexx[], yf = Rexx[], xprecision = 3, yprecision = 5) -
public static signals IllegalArgumentException, FileNotFoundException, IOException
 
if xf.length > yf.length then signal IllegalArgumentException('Y array must be at least as long as X array')
 
fw = BufferedWriter(OutputStreamWriter(FileOutputStream(outFile)))
 
loop i_ = 0 to xf.length - 1
row = xf[i_].format(null, xprecision, null, xprecision).left(15) yf[i_].format(null, yprecision, null, yprecision)
(Writer fw).write(String row)
fw.newLine
end i_
fw.close
 
return
 
Output:
1.000           1.00000
2.000           1.41421
3.000           1.73205
1.000E+11       3.16228E+5

[edit] NewLISP

; file:   write-float-array.lsp
; url: http://rosettacode.org/wiki/Write_float_arrays_to_a_text_file
; author: oofoe 2012-01-30
 
; The "transpose" function is used to flip the joined lists around so
; that it's easier to iterate through them together.
 
(define (write-float-array x xp y yp filename)
(let ((f (format "%%-10.%dg %%-10.%dg" xp yp))
(o (open filename "write")))
(dolist (v (transpose (list x y)))
(write-line o (format f (v 0) (v 1))))
(close o)
))
 
; Test
 
(write-float-array
'(1 2 3 1e11) 3
'(1 1.4142135623730951 1.7320508075688772 316227.76601683791) 5
"filename.chan")
 
(println "File contents:")
(print (read-file "filename.chan"))
 
(exit)
Output:
File contents:
1          1         
2          1.4142    
3          1.7321    
1e+011     3.1623e+005

[edit] Nimrod

import strutils, math, sequtils
 
const
outFileName = "floatarr2file.txt"
 
proc sqrt*(x: int64): float {.importc: "sqrt", header: "<math.h>".}
 
const
xprecision = 3
yprecision = 5
 
var a: seq[int64] = @[int64(1), 2, 3, 100_000_000_000]
var b: seq[float] = @[sqrt(a[0]), sqrt(a[1]), sqrt(a[2]), sqrt(a[3])]
var c = zip(a,b)
var res: string = ""
for t in c:
res.add($formatFloat(float(t.a),ffDefault,xprecision) & "\t" & $formatFloat(t.b,ffDefault,yprecision) & "\n")
 
writeFile(outFileName,res)
var res2 = readFile(outFileName)
echo(res2)
Output:
1.00	1.0000
2.00	1.4142
3.00	1.7321
1.00e+11	3.1623e+05

[edit] OCaml

let write_dat filename x y ?(xprec=3) ?(yprec=5) () =
let oc = open_out filename in
let write_line a b = Printf.fprintf oc "%.*g\t%.*g\n" xprec a yprec b in
List.iter2 write_line x y;
close_out oc

Example usage

# let x = [1.0; 2.0; 3.0; 1e11];;
val x : float list = [1.; 2.; 3.; 100000000000.]
# let y = List.map sqrt x;;
val y : float list =
  [1.; 1.41421356237309515; 1.73205080756887719; 316227.766016837908]
# write_dat "sqrt.dat" x y ();;
- : unit = ()
# let ic = open_in "sqrt.dat";;
val ic : in_channel = <abstr>
# try
    while true do
      print_endline (input_line ic)
    done
  with End_of_file -> ();;
1	1
2	1.4142
3	1.7321
1e+11	3.1623e+05
- : unit = ()

[edit] PARI/GP

Works with: PARI/GP version 2.5.0 and above
f(x,pr)={
Strprintf(if(x>=10^pr,
Str("%.",pr-1,"e")
,
Str("%.",pr-#Str(x\1),"f")
),x)
};
wr(x,y,xprec,yprec)={
for(i=1,#x,
write("filename",f(x[i],xprec),"\t",f(y[i],yprec))
)
};

[edit] Pascal

Program WriteNumbers;
 
const
x: array [1..4] of double = (1, 2, 3, 1e11);
xprecision = 3;
yprecision = 5;
baseDigits = 7;
 
var
i: integer;
filename: text;
 
begin
assign (filename, 'filename');
rewrite (filename);
for i := 1 to 4 do
writeln (filename, x[i]:baseDigits+xprecision, sqrt(x[i]):baseDigits+yprecision);
close (filename);
end.

File contents

 1.00E+000 1.0000E+000
 2.00E+000 1.4142E+000
 3.00E+000 1.7321E+000
 1.00E+011 3.1623E+005

[edit] Perl

sub writedat {
my ($filename, $x, $y, $xprecision, $yprecision) = @_;
open FH, ">", $filename or die "Can't open file: $!";
printf FH "%.*g\t%.*g\n", $xprecision||3, $x->[$_], $yprecision||5, $y->[$_] for 0 .. $#$x;
close FH;
}
 
my @x = (1, 2, 3, 1e11);
my @y = map sqrt, @x;
 
writedat("sqrt.dat", \@x, \@y);

File contents

1	1
2	1.4142
3	1.7321
1e+11	3.1623e+05

[edit] Perl 6

Translation of: Perl
sub writedat ( $filename, @x, @y, $x_precision = 3, $y_precision = 5 ) {
my $fh = open $filename, :w;
 
for @x Z @y -> $x, $y {
$fh.printf: "%.*g\t%.*g\n", $x_precision, $x, $y_precision, $y;
}
 
$fh.close;
}
 
my @x = 1, 2, 3, 1e11;
my @y = @x.map({.sqrt});
 
writedat( 'sqrt.dat', @x, @y );

File contents

1	1
2	1.4142
3	1.7321
1e+11	3.1623e+05

[edit] PicoLisp

An exponential format like "1e11" is not supported

(setq *Xprecision 3  *Yprecision 5)
 
(scl 7)
(mapc
'((X Y)
(prinl
(round X *Xprecision)
" "
(round Y *Yprecision) ) )
(1.0 2.0 3.0)
(1.0 1.414213562 1.732050807) )
Output:
1.000  1.00000
2.000  1.41421
3.000  1.73205

[edit] PL/I

 
declare X(5) float (9) initial (1, 2, 3, 4, 5),
Y(5) float (18) initial (9, 8, 7, 6, 1e9);
declare (x_precision, y_precision) fixed binary;
open file (out) title ('/OUT.TXT,type(text),recsize(100)');
x_precision = 9;
y_precision = 16;
put file (out) edit ((X(i), Y(i) do i = 1 to 5))
(skip, e(16, x_precision),
x(2), e(20, y_precision) );
 

[edit] PureBasic

#Size = 4
 
DataSection
Data.f 1, 2, 3, 1e11 ;x values, how many values needed is determined by #Size
EndDataSection
 
Dim x.f(#Size - 1)
Dim y.f(#Size - 1)
 
Define i
For i = 0 To #Size - 1
Read.f x(i)
y(i) = Sqr(x(i))
Next
 
Define file$, fileID, xprecision = 3, yprecision = 5, output$
 
file$ = SaveFileRequester("Text file for float data", "xydata.txt","Text file | *.txt", 0)
If file$
fileID = OpenFile(#PB_Any, file$)
If fileID
For i = 0 To #Size - 1
output$ = StrF(x(i), xprecision) + Chr(9) + StrF(y(i), yprecision)
WriteStringN(fileID, output$)
Next
CloseFile(fileID)
EndIf
EndIf
Output:
to text file:
1.000	1.00000
2.000	1.41421
3.000	1.73205
99999997952.000	316227.75000

[edit] Python

Works with: Python version 2.6
import itertools
def writedat(filename, x, y, xprecision=3, yprecision=5):
with open(filename,'w') as f:
for a, b in itertools.izip(x, y):
print >> f, "%.*g\t%.*g" % (xprecision, a, yprecision, b)

Example usage

>>> import math
>>> x = [1, 2, 3, 1e11]
>>> y = map(math.sqrt, x)
>>> y
[1.0, 1.4142135623730951, 1.7320508075688772, 316227.76601683791]
>>> writedat("sqrt.dat", x, y)
>>> # check
...
>>> for line in open('sqrt.dat'):
... print line,
...
1 1
2 1.4142
3 1.7321
1e+011 3.1623e+005
Works with: Python version 3
def writedat(filename, x, y, xprecision=3, yprecision=5):
with open(filename,'w') as f:
for a, b in zip(x, y):
print("%.*g\t%.*g" % (xprecision, a, yprecision, b), file=f)
#or, using the new-style formatting:
#print("{1:.{0}g}\t{3:.{2}g}".format(xprecision, a, yprecision, b), file=f)

[edit] R

writexy <- function(file, x, y, xprecision=3, yprecision=3)
{
#Format inputs as required, and join together
fx <- formatC(x, digits=xprecision, format="g", flag="-")
fy <- formatC(y, digits=yprecision, format="g", flag="-")
dfr <- data.frame(fx, fy)
#Write to file. Note that this encloses the formatted number in quotes,
write.table(dfr, file=file, sep="\t", row.names=FALSE)
#... so we have to process the output
str <- readLines(file)
writeLines(gsub('"', '', str), file)
}
 
 
x <- c(1, 2, 3, 1e11)
y <- sqrt(x)
writexy('test.txt', x, y, yp=5)

[edit] Racket

 
#lang racket
 
(define xs '(1.0 2.0 3.0 1.0e11))
(define ys '(1.0 1.4142135623730951 1.7320508075688772 316227.76601683791))
 
(define xprecision 3)
(define yprecision 5)
 
(with-output-to-file "some-file" #:exists 'truncate
(λ() (for ([x xs] [y ys])
(displayln (~a (~r x #:precision xprecision)
" "
(~r y #:precision yprecision))))))
 
#|
The output is not using exponenets as above, but that's not needed
since Racket can read these numbers fine:
 
1 1
2 1.41421
3 1.73205
100000000000 316227.76602
|#
 

[edit] Raven

3 as $xprecision
5 as $yprecision
 
[ ] as $results
 
[ 1 2 3 1e11 ] as $a
 
group
$a each sqrt
list as $b
 
# generate format specifier "%-8.3g %.5g\n"
"%%-8.%($xprecision)dg %%.%($yprecision)dg\n" as $f
 
define print2 use $v1, $v2, $f
$v2 1.0 prefer $v1 1.0 prefer $f format $results push
 
4 each as $i
$f $b $i get $a $i get print2
$results "" join "results.dat" write
Output:

results.dat file contains:

1        1
2        1.4142
3        1.7321
1e+11    3.1623e+05

[edit] REXX

/*REXX program writes  two arrays  to a file  with  limited precision,  */
numeric digits 1000 /* ··· but allow a huge # of digits. */
outfid = 'OUTPUT.TXT' /*file name structure is OS dependent*/
x. =  ; y. =
x.1 = 1  ; y.1 = 1
x.2 = 2  ; y.2 = 1.4142135623730951
x.3 = 3  ; y.3 = 1.7320508075688772
x.4 = 1e11  ; y.4 = 316227.76601683791
xPrecision = 3 /*precision for the X numbers. */
yPrecision = 5 /* " " " Y " */
padding=left('',4) /*number of blanks between cols. */
do j=1 while x.j\=='' /*process all numbers.*/
x.j=req_way(x.j, xPrecision) /*format the X numbers*/
y.j=req_way(y.j, yPrecision) /* " " Y " */
aLine=translate(x.j || padding || y.j, 'e', "E")
say aLine /*display to terminal.*/
call lineout outfid,aLine /*write to disk file. */
end /*j*/
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────REQ_WAY (required) subroutine───────*/
req_way: procedure; parse arg a,p; numeric digits p; a=format(a,,p)
parse var a mantissa 'E' expon /*obtain the exponent digits. */
parse var mantissa int '.' fract /* " " integer & fraction. */
fract=strip(fract, 'T', 0) /*strip trailing zeros from frac.*/
if fract\=='' then fract='.'fract /*if fraction digits, add decimal*/
if expon\=='' then expon='E'expon /* " exponent " " an E */
a=int || fract || expon /*format # according to the rules*/
if datatype(a,'W') then return format(arg(1)/1,,0) /*whole number? */
return format(arg(1)/1,,,3,0) /*use 3 dec digs*/
Output:
1    1
2    1.4142
3    1.7321
1e+011    3.1623e+005

[edit] RLaB

In RLaB this task can be done in two ways:

1. Direct writing of the numerical data to the file of an array using function writem. Here the writing format is specified using the global property that is accessible through function format.

 
>> x = rand(10,1); y = rand(10,1);
>> writem("mytextfile.txt", [x,y]);
 

2. Converting the numerical data to text, and then writing the text to the file, using the same function writem. Here, the writing format is specified through text function, and the result is written as a plain string matrix.

 
>> x = rand(10,1); y = rand(10,1);
>> s = text( [x,y], "%10.8f" );
>> writem("mytextfile.txt", s);
 

Please note, writem function in RLaB can operate in two-fold fashion. RLaB keeps track of the open files that were created using the built-in function open.

If user writes the data to a file using open followed by writem then RLaB opens the file in append mode if it already hasn't been opened. If it has been, then the command open is ignored (say in batch mode). Then, each successive call to writem appends newest data to the end of the file while keeping the file open. RLaB will close the file (and OS will flush its file buffer) upon the command close.

If user writes the data to a file by using only writem then the RLaB temporarily opens the file, writes the data to it, and then closes the file. Successive calls to writem in this mode will erase the previous content of the file.

[edit] Ruby

# prepare test data
x = [1, 2, 3, 1e11]
y = x.collect { |xx| Math.sqrt xx }
xprecision = 3
yprecision = 5
 
# write the arrays
open('sqrt.dat', 'w') do |f|
x.zip(y) { |xx, yy| f.printf("%.*g\t%.*g\n", xprecision, xx, yprecision, yy) }
end
 
# print the result file
open('sqrt.dat', 'r') { |f| puts f.read }

Result:

1       1
2       1.4142
3       1.7321
1e+11   3.1623e+05

[edit] Run BASIC

x$ = "1, 2, 3, 1e11"
y$ = "1, 1.4142135623730951, 1.7320508075688772, 316227.76601683791"
 
open "filename" for output as #f ' Output to "filename"
for i = 1 to 4
print #f, using("##############.###",val(word$(x$,i,",")));"|";using("#######.#####",val(word$(y$,i,",")))
next i
close #f
Output:
             1.000|      1.00000
             2.000|      1.41421
             3.000|      1.73205
  100000000000.000| 316227.76602

[edit] SAS

data _null_;
input x y;
file "output.txt";
put x 12.3 " " y 12.5;
cards;
1 1
2 1.4142135623730951
3 1.7320508075688772
1e11 316227.76601683791
;
run;

[edit] Scala

Library: Scala
import java.io.{File, FileWriter, IOException}
 
object FloatArray extends App {
val x: List[Float] = List(1f, 2f, 3f, 1e11f)
 
def writeStringToFile(file: File, data: String, appending: Boolean = false) =
using(new FileWriter(file, appending))(_.write(data))
 
def using[A <: {def close() : Unit}, B](resource: A)(f: A => B): B =
try f(resource) finally resource.close()
 
try {
val file = new File("sqrt.dat")
using(new FileWriter(file))(writer => x.foreach(x => writer.write(f"$x%.3g\t${math.sqrt(x)}%.5g\n")))
} catch {
case e: IOException => println(s"Running Example failed: ${e.getMessage}")
}
}

[edit] Seed7

The library math.s7i defines the function sqrt. The operators sci and exp (defined in float.s7i) support writing floating point numbers in scientific notation.
$ include "seed7_05.s7i";
include "float.s7i";
include "math.s7i";
 
const proc: main is func
local
const array float: numbers is [] (1.0, 2.0, 3.0, 1.0e11);
var float: aFloat is 0.0;
var file: aFile is STD_NULL;
begin
aFile := open("filename", "w");
for aFloat range numbers do
writeln(aFile, aFloat sci 3 exp 2 <& " " <& sqrt(aFloat) sci 5 exp 2);
end for;
close(aFile);
end func;
Result file filename:
1.000e+00 1.00000e+00
2.000e+00 1.41421e+00
3.000e+00 1.73205e+00
1.000e+11 3.16228e+05

[edit] Standard ML

fun writeDat (filename, x, y, xprec, yprec) = let
val os = TextIO.openOut filename
fun write_line (a, b) =
TextIO.output (os, Real.fmt (StringCvt.GEN (SOME xprec)) a ^ "\t" ^
Real.fmt (StringCvt.GEN (SOME yprec)) b ^ "\n")
in
ListPair.appEq write_line (x, y);
TextIO.closeOut os
end;

Example usage

- val x = [1.0, 2.0, 3.0, 1e11];
val x = [1.0,2.0,3.0,100000000000.0] : real list
- val y = map Math.sqrt x;
val y = [1.0,1.41421356237,1.73205080757,316227.766017] : real list
- writeDat ("sqrt.dat", x, y, 3, 5);
val it = () : unit
- val is = TextIO.openIn "sqrt.dat";
val is = - : TextIO.instream
- print (TextIO.inputAll is);
1.0	1.0
2.0	1.4142
3.0	1.7321
1E11	3.1623E05
val it = () : unit

[edit] Tcl

set x {1 2 3 1e11}
foreach a $x {lappend y [expr {sqrt($a)}]}
set fh [open sqrt.dat w]
foreach a $x b $y {
puts $fh [format "%.*g\t%.*g" $xprecision $a $yprecision $b]
}
close $fh
 
set fh [open sqrt.dat]
puts [read $fh [file size sqrt.dat]]
close $fh
Output:
1	1
2	1.4142
3	1.7321
1e+011	3.1623e+005

[edit] zkl

var xs=T(1,2,3,1e11);
xs.pump(File("floatArray","w").writeln,
fcn(x){ "%.3g\t%.5g".fmt(x,x.toFloat().sqrt()) });

or

xs:=T(1.0,2.0,3.0,1e11); ys:=xs.apply("sqrt");
f:=File("floatArray","w");
foreach x,y in (xs.zip(ys)){ f.writeln("%.3g\t%.5g".fmt(x,y)); }
f.close();
Output:
$ cat floatArray 
1	1
2	1.4142
3	1.7321
1e+11	3.1623e+05

[edit] ZX Spectrum Basic

The ZX Spectrum has a dedicated file format for floating point arrays. Although this format is not a text file, it would be the usual format for writing such data to a file on a ZX Spectrum. Here we write the contents of the array g() to a file:

SAVE "myarray" DATA g()
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