Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks
I have the following script, which reads a tab-delimited file, where the $snp variable is the ID of each line.
What I am trying to do (unsuccessfully so far) is to only increment the $counter variable if the $snp changes, else, it should stay as it was previously, i.e. all lines with the same $snp should have the same $counter in front.
Can you fix my error please?
$counter=0;
%hash=();

while(<>)
{
    $line=$_;
        chomp $line;
    @split_line=split(/\t/, $line);

    $snp=$split_line[0];
    $x11=$split_line[1];
    $x12=$split_line[2];
    $x22=$split_line[3];
    $gen11=$split_line[4];
    $gen12=$split_line[5];
    $gen22=$split_line[6];
    $sd11=$split_line[7];
    $sd12=$split_line[8];
    $sd22=$split_line[9];
    $study=$split_line[10];
    $snp1=$split_line[11];
    $x33=$split_line[12];
    $x34=$split_line[13];
    $x44=$split_line[14];
    $gen33=$split_line[15];
    $gen34=$split_line[16];
    $gen44=$split_line[17];
    $sd33=$split_line[18];
    $sd34=$split_line[19];
    $sd44=$split_line[20];
    $study1=$split_line[21];
    $a1=$split_line[22];
    $a2=$split_line[23];

    if($x11 eq 'NA')     {$x11='.';}
    if($x12 eq 'NA')     {$x12='.';}
    if($x22 eq 'NA')     {$x22='.';}
    if($gen11 eq 'NA')     {$gen11='.';}
    if($gen12 eq 'NA')     {$gen12='.';}
    if($gen22 eq 'NA')     {$gen22='.';}
    if($sd11 eq 'NA')     {$sd11='.';}
    if($sd12 eq 'NA')     {$sd12='.';}
    if($sd22 eq 'NA')     {$sd22='.';}
    if($x33 eq 'NA')     {$x33='.';}
    if($x34 eq 'NA')     {$x34='.';}
    if($x44 eq 'NA')     {$x44='.';}
    if($gen33 eq 'NA')     {$gen33='.';}
    if($gen34 eq 'NA')     {$gen34='.';}
    if($gen44 eq 'NA')     {$gen44='.';}
    if($sd33 eq 'NA')     {$sd33='.';}
    if($sd34 eq 'NA')     {$sd34='.';}
    if($sd44 eq 'NA')     {$sd44='.';}

    $rest=$x11."\t".$x12."\t".$x22."\t".
    $gen11."\t".$gen12."\t".$gen22."\t".
    $sd11."\t".$sd12."\t".$sd22."\t".
    $study."\t".$snp1."\t".
    $x33."\t".$x34."\t".$x44."\t".
    $gen33."\t".$gen34."\t".$gen44."\t".
    $sd33."\t".$sd34."\t".$sd44."\t".
    $study1."\t".$a1."\t".$a2."\n";

    if(not exists($hash{$snp}))
    {
        $counter++;
        print $counter."\t".$snp."\t".$rest;
    }

    else
    {
        print $counter."\t".$snp."\t".$rest;
    }

}

[download]

Replies are listed 'Best First'.
Re: only increment counter if the ID has not been seen before
by toolic (Bishop) on Mar 12, 2015 at 01:15 UTC
    You need to populate the hash inside the loop somehow. Here is one way: 
    use warnings;
use strict;

my $counter = 0;
my %hash;
while (<DATA>) {
    my @splits = split;
    my $snp = $splits[0];
    $counter++ if not exists $hash{$snp};
    print "$counter $snp\n";
    $hash{$snp}++;
}

__DATA__
foo    abc
foo    cde
bar    xyz

    [download]

    Prints: 

    1 foo
1 foo
2 bar

    [download]
[reply]
[d/l]
[select]
      The OP wanted the same number in front of each occurence of the same ID, not a slowly increasing number counting different IDs so far. This can be achieved with a hash storing unique numbers rather than repetition counts. 
      use warnings;
use strict;

my $counter = 0;
my %hash;
while (<DATA>) {
    my @splits = split;
    my $snp = $splits[0];
    $hash{$snp} ||= ++$counter;
    print "$hash{$snp} $snp\n";
}

__DATA__
foo     abc
foo     cde
bar     xyz
foo     hij

      [download]
      This should output: 
      1 foo
1 foo
2 bar
1 foo

      [download]
      ... rather than: 
      1 foo
1 foo
2 bar
2 foo

      [download]
[reply]
[d/l]
[select]
      Ah, I just needed this thing then: $hash{$snp}++;
      Damn! Thank you very much!
[reply]
[d/l]

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