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Top Forums Shell Programming and Scripting Get 20% of lines in File randomly Post 302707225 by Lem on Friday 28th of September 2012 07:39:08 AM
Old 09-28-2012
If I'm right your problem is to randomly generate N integers in the range [1;M], where M is the number of lines in the file, and N is a rounded percentage of M.

Before going on: are repetitions allowed? In other words, may a number (a line in the file) be randomly selected more than once?

And: what are your shell and OS?

EDIT: solution proposed

However, this is a possible solution working on linux/bash, with repetitions not allowed:
Code:
#!/bin/bash
range=$(wc -l "$1" | cut -d " " -f1)
(( $range > 32768 )) && exit              ### max number of lines for this script: 32768
percent=$2                                ### set this  as you like, [1-100]
(( 0 < $2 )) && (( $2 < 101 )) || exit
lim=$(( $range * $percent / 100 ))
for ((i=0;i<lim;i++)); do
        num=$(( $RANDOM % $range + 1 ));
        arr[$i]=$num;
        for ((j=0;j<i;j++)); do
                (( ${arr[$j]} == $num )) && {
                        let i--
                        break; }
        done
done

for linenum in "${arr[@]}"; do
        line=$(sed -n "$linenum p" "$1")
        ### your stuff here, for example: ###
        echo "$linenum"$'\t'"### $line"
done

exit 0

Usage:
Code:
lem@biggy:/tmp$ ./file2 file2 30
6	### lim=$(( $range * $percent / 100 ))
19	###         ### your stuff here, for example: ###
11	###                 (( ${arr[$j]} == $num )) && {
10	###         for ((j=0;j<i;j++)); do
5	### (( 0 < $2 )) && (( $2 < 101 )) || exit
4	### percent=$2                                ### set this  as you like, [1-100]

--
Bye

Last edited by Lem; 09-28-2012 at 11:36 AM.. Reason: Solution proposed
This User Gave Thanks to Lem For This Post:
 

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PGASetRealInitPercent(2)					      PGAPack						  PGASetRealInitPercent(2)

NAME
PGASetRealInitPercent - sets the upper and lower bounds for randomly initializing real-valued genes. DESCRIPTION
For each gene these bounds define an interval from which the initial allele value is selected uniformly randomly. With this routine the user specifies a median value and a percent offset for each allele. INPUT PARAMETERS
ctx - context variable median - an array containing the mean value of the interval percent - an array containing the percent offset to add and subtract to the median to define the interval OUTPUT PARAMETERS
none SYNOPSIS
#include "pgapack.h" void PGASetRealInitPercent(ctx, median, percent) PGAContext *ctx double *median double *percent LOCATION
real.c EXAMPLE
Set the initialization routines to select a value for each real-valued gene i uniformly randomly from the interval [i-v,i+v], where $v = i/2$. Assumes all strings are the same length. PGAContext *ctx; double *median, *percent; int i, stringlen; : stringlen = PGAGetStringLength(ctx); median = (double *) malloc(stringlen*sizeof(double)); percent = (double *) malloc(stringlen*sizeof(double)); for(i=0;i<stringlen;i++) { median[i] = (double) i; percent[i] = 0.5; } PGASetRealInitPercent(ctx, median, percent); 05/01/95 PGASetRealInitPercent(2)
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