Need help with Perl

[Fad2012]

Hello guys

I have the following dataset

ID Kind
259 P0_P2
260 P0_P2
57 P2
58 P2
59 P2
60 P2
61 P2
62 P2

I am trying to write a Perl code to pick the kind ID of "P0_P2" and attach it to the IDs of the rest of the kinds. So the expected results will be:

Anc Child
259 57
259 58
259 59
259 60
259 61
259 62
259 57
260 58
260 59
260 60
260 61
260 62

I wrote the following Perl code, but not sure why it is not working. The code takes an external tab delimited file, which contains the data.

#!/usr/bin/perl

my $firFile = "$ARGV[0]";
open (NGS, $firFile);
my $Ancestor="";
my $Childern="";
my $starting_childern = 0;

while (<NGS>) {
chomp;

my @fields = split ('\t', $_);

if ($fields[1] eq "P0_P2") {

$starting_childern = 1;
$Ancestor = $fields[0];

print "$Ancestor\n";
}

elsif ($starting_childern == 1) {

$Childern = $fields[0];
if ($fields[1] ne "P0_P2"){
print "$Ancestor \t $Childern\n";

}

}

}
close (NGS);

Could you please help me with this
Many thanks

[Fad2012]

PS.
The code is printing nothing upon execution!

[SNPsaurus]

I'd add some informative print statements like print "fields[0] fields[1] in Ancestor if block\n" at different locations to see what your computer is reading in.

I was going to say, "oh it is a typo that you spelled children childern" but you were consistent the whole time!".

[Fad2012]

Thank you SNPsaurus. I am not sure what is going on with this code.
Any suggestion anyone
Many thanks

[SNPsaurus]

Did you try to add some informative print statements to see what information is in your variables?

[Fad2012]

Hi SNPsaurus

Yes, I tried. The only way it printed something when I put

print "fields[0] \n"

Just after the split command. I tried to play with many other things with no positive results. For example, I tried to change the variable types from my $Ancestor=""; to my $Ancestor=0;. I also tried to move print "$Ancestor \t $Childern\n"; around the code, but nothing worked...

[SNPsaurus]

What did it print? It is hard to help when you provide so little information. Did it print "259 P0_P2" or the proper "259"? After the split, add:
print "f0 $fields[0]\tf1 $fields[1]\n";

What is the output from that?

[Fad2012]

Thank you very much SNPsaurus.

I removed the column titles for now. So I removed the ID nad the Kind from the table. WhenI use print "f0 $fields[0]\tf1 $fields[1]\n"; It prints the following

f0 259 f1 P0_P2
f0 260 f1 P0_P2
f0 57 f1 P2
f0 58 f1 P2
f0 59 f1 P2
f0 60 f1 P2
f0 61 f1 P2
f0 62 f1 P2

When I use:
print "f0 $fields[0]\n"; it prints:

f0 259
f0 260
f0 57
f0 58
f0 59
f0 60
f0 61
f0 62

In both cases it should be after the split line

Many thanks

[SNPsaurus]

OK, so the split works. Let's see if your if statement works. After if ($fields[1] eq "P0_P2") {
put:
print "in if statement\n";

[Fad2012]

OK, so the split works. Let's see if your if statement works. After if ($fields[1] eq "P0_P2") {
put:
print "in if statement\n";

Nothing appeared, so that means the statement is not working?

[Fad2012]

Well, when I replaced the "eq" with "=~" things worked and it printed:
in if statement
in if statement

It seems that the eq is not working

[SNPsaurus]

Right. I wonder if your input file has DOS or other funny line breaks/ carriage returns at the end. That used to be the source of most of my woes.

You could try chop; chop; instead of chomp; I'd print field[0] and [1] again to see if it is trimming your actual data instead of getting rid of both line end characters.

You could also do

local $/ = "\n";

for my $line (<NGS>) {
$line =~ s/\r?\n$//;

Which should get rid end of line weirdness. You could re-type your if statement to make sure P0 is not PO or other random typos.

[Fad2012]

Thank you

I really appreciate your help, I will play around with it and will let you know

Many thanks
Fadi