Re: Deconvolutinng FastQ files

[BrowserUk]

Try this. It should take around 40 minutes for 34GB:

#! perl -sw
use strict;

my %outFHs = map {
   open my $fh, '>', "$_.fastQ" or die $!;
   $_ => $fh;
} qw[ TTGT GGTT ACCT ];

until( eof() ) {
    my @lines = map scalar <>, 1 .. 4;
    my $barcode = substr $lines[1], 0, 9;
    my $tag = substr $barcode, 3, 4;

    print { $outFHs{ $tag } } @lines;
}
__END__
usage:
thisScript theBigfile.fastQ

## outputs to TTGT.fastQ GGTT.fastQ ACCT.fastQ

[snakebites]

Thank you browseruk. Wow.. I didn't realise you could sort out the whole thing using less than 2 dozen lines of perl script :O. I am so glad I asked. However, when testing the script out with my fastq files I got three files with a few records in each, but then the script stopped and I got the following error message:

Use of uninitialized value within %outFHs in ref-to-glob cast at Sort.pl line 14, <> line 120.

Can't use string ("") as a symbol ref while "strict refs" in use at Sort.pl line 14, <> line 120.

How can I debug this? I guess this has to do with my records? Thank you.

[BrowserUk]

Line 120 of your data file contains a record where the key field (characters 4 through 7) are not one of "TTGT" "GGTT" "ACCT"

To handle that, try this modified version:

#! perl -sw
use strict;

my %outFHs = map {
   open my $fh, '>', "$_.fastQ" or die $!;
   $_ => $fh;
} qw[ TTGT GGTT ACCT other ];

until( eof() ) {
    my @lines = map scalar <>, 1 .. 4;
    my $barcode = substr $lines[1], 0, 9;
    my $tag = substr $barcode, 3, 4;

    print { $outFHs{ $tag } // $outFGs{ other } } @lines;
}
__END__
usage:
thisScript theBigfile.fastQ

## outputs to TTGT.fastQ GGTT.fastQ ACCT.fastQ
## Unrecognised records are put into "other.fastQ"

[snakebites]

I see. That makes sense since the machine that spits the results makes about 4% errors reading the first few letters just by manually inspecting my files, so sometimes TTGT might come out as TGGT or GGTT might come out as GGTA which are neither of the three barcodes I am after. I guess with the new script you posted I need to specify 'other' with all possible combination of the four letters that might be in my fastq to make sure that the script doesn't stall. Thank you again browseruk.

[snakebites]

I have just realised there was a simple typo in the code ver2.0, but ver 2 and ver 3 worked really well :O. You are an amazing perlmonk! Browseruk, we will be happy to acknowledge your contribution with the script in future publications for this work. I will PM you.