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Re: grabbing random n rows from a file

by Hue-Bond (Priest)
on Jul 18, 2006 at 21:58 UTC ( [id://562146]=note: print w/replies, xml ) Need Help??


in reply to grabbing random n rows from a file

This reads $j lines, then skips until $m is reached, then starts reading again. Prints to STDOUT, not to a new file. But that isn't your main concern, is it? ;^).

#!/usr/bin/perl use warnings; use strict; my $m = 3; ## lines in each set my $j = 2; ## lines that should get printed my $i = 0; while (<DATA>) { $i++; print; ## skip if ($i == $j) { <DATA> while $i++ != $m; $i = 0; } } __DATA__ foo 1 2 3 foo 2 3 4 foo 4 5 6 bar a b c bar b c d bar c d e baz q w e baz w e r baz e r t

Update: Oops, missed the "random" bit. Let's try this:

#!/usr/bin/perl use warnings; use strict; use List::Util qw/shuffle/; my $m = 3; my $j = 2; MAIN: while (1) { my @set; for (my $i = 0; $i < $m ; $i++) { last MAIN unless defined ($_ = <DATA>); push @set, $_; } for ((shuffle @set)[0..$j-1]) { print; } } __DATA__ foo 1 2 3 foo 2 3 4 foo 4 5 6 bar a b c bar b c d bar c d e baz q w e baz w e r baz e r t

--
David Serrano

Replies are listed 'Best First'.
Re^2: grabbing random n rows from a file
by ikegami (Patriarch) on Jul 18, 2006 at 22:50 UTC
    According to the OP's "Update 2", m is neither neither known nor constant. japhy made the same incorrect assumption above.

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