On Mon, 30 Sep 2002, Paul and Joann Van Dalen wrote:
> Hi all,
>
> Given an input file that has the following records:
>
> 123 ABC XX112 YYYY Zzzzzzzzzz
> 123 DEF XX113 WWWW Zzzzzzzzz
> 123 EEF XX112 YYYY Zzzzzzzzzz
> 444 ccc vvbfd QQQQ ccccccccc
> 444 CCd vvbfd QQQQ ccccccccc
> 444 ddd ssddd QQQQ xxxxxxxx
>
> I need to focus on the first column (the input file is already sorted on
> that field) and, grouped by the first column, pull out
> the first record of that group.
> e.g., I would need to have the following from the above as output:
>
> 123 ABC XX112 YYYY Zzzzzzzzzz
> 444 ccc vvbfd QQQQ ccccccccc
>
> I believe I'd need something like a hash, where for every record within
> a group defined by the common value of the first column, I take the
> numerically first occurance of that group, but I don't know how to do
> that in Perl. Would it take a loop for each group within the loop for
> the entire file??
You are on the right track, you will have to do something like this
open (INPUTFILE, $your_input_file) or die "Error opening $your_input_file: $!\n";
my %uniq_hash;
while (<INPUTFILE>) {
(my $first_field) = (split)[0];
unless ($uniq_hash{$first_field}++) {
# The first check will pass and increment the key value
# All further checks will fail
print;
}
}
close (INPUTFILE);
In principle this quite similar to
perldoc -q 'How can I remove duplicate elements from a list or array?'
>
> Thanks very much,
> Paul
>
>
>
>
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