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You can stream it and prevent memory hogs on big data. Additionally, install Text::CSV_XS for speed

use Text::CSV_XS "csv"; my %sums; # Column sums. $sum{column} += $value my @head; my @pats; csv (in => "input.csv", out => undef, bom => 1, kh => \@head, on_in => + sub { my ($csv, $row) = @_; unless (@pats) { # Fetch the "patN" column names, in order. This works # for single digit "patN" names, as that was your # example. Multi-digit names will require a more complex # sort, left as an exercise to the reader. # XXX @pats = sort { grep m/^pat\d+$/ } @head; @pats = sort grep m/^pat\d+$/ => @head; # This line fixed } for (@{$row}{@pats}) { # You are now iterating over every patN value, # in order. Perform your transformation } # Just an example. $sums{$_} += $row->{$_} for @pats; });

update: I changed the grep line which I blindly copied from the original code

Enjoy, Have FUN! H.Merijn

In reply to Re^2: Perl script for the post processing of one CSV file by Tux
in thread Perl script for the post processing of one CSV file by kshitij

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