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Top Forums UNIX for Dummies Questions & Answers How to randomly select lines from a text file Post 302720879 by alister on Wednesday 24th of October 2012 06:28:29 PM
Old 10-24-2012
Quote:
Originally Posted by Corona688
Code:
awk 'NR==FNR { B++; next }
(NR != FNR) && (!Z) {
        srand();
        if(Z < 200) exit(1); # Too few lines
        for(N=1; N<=200; N++)
        {
                V=sprintf("%d", (rand()*B)+1)+0;
                if(!(V in A)) { A[V]=1; N++ }
        }
        Z=1
} NR in A' inputfile inputfile

Looks like there are a couple of bugs there. The first, a typo of Z for B, always exits before selecting anything. The second, the for-loop post-increment expression, can cause the algorithm to yield anywhere between 1 and 200 lines.

Probably no need to fix it since Scrutinizer's first example in post #5 is a correct implementation of the same approach.

Regards,
Alister

---------- Post updated at 06:28 PM ---------- Previous update was at 06:26 PM ----------

With regard to all of the AWK suggestions, without knowing exactly how the script is to be used, it's possible that all of the recommendations are inadequate. Nearly every awk srand implementation's default seed is the number of seconds since the epoch. Successive or simultaneous runs could yield identical results. May or may not be an issue. We don't have sufficient information to make that determination. Just a head's up for the OP.

If it is an issue, more information would be required to determine a robust seed expression.

Regards,
Alister
This User Gave Thanks to alister For This Post:
 

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Imager::Color::Float(3pm)				User Contributed Perl Documentation				 Imager::Color::Float(3pm)

NAME
Imager::Color::Float - Rough floating point sample color handling SYNOPSIS
$color = Imager::Color->new($red, $green, $blue); $color = Imager::Color->new($red, $green, $blue, $alpha); $color = Imager::Color->new("#C0C0FF"); # html color specification $color->set($red, $green, $blue); $color->set($red, $green, $blue, $alpha); $color->set("#C0C0FF"); # html color specification ($red, $green, $blue, $alpha) = $color->rgba(); @hsv = $color->hsv(); # not implemented but proposed $color->info(); DESCRIPTION
This module handles creating color objects used by Imager. The idea is that in the future this module will be able to handle color space calculations as well. A floating point Imager color consists of up to four components, each in the range 0.0 to 1.0. Unfortunately the meaning of the components can change depending on the type of image you're dealing with: o for 3 or 4 channel images the color components are red, green, blue, alpha. o for 1 or 2 channel images the color components are gray, alpha, with the other two components ignored. An alpha value of zero is fully transparent, an alpha value of 1.0 is fully opaque. METHODS
new This creates a color object to pass to functions that need a color argument. set This changes an already defined color. Note that this does not affect any places where the color has been used previously. rgba() This returns the red, green, blue and alpha channels of the color the object contains. info Calling info merely dumps the relevant color to the log. AUTHOR
Arnar M. Hrafnkelsson, addi@umich.edu And a great deal of help from others - see the "README" for a complete list. SEE ALSO
Imager(3), Imager::Color. http://imager.perl.org/ perl v5.14.2 2011-06-06 Imager::Color::Float(3pm)
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