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how to merge the files of DNA sequences?

by newperler (Initiate)
on Jul 24, 2004 at 07:54 UTC ( #377103=perlquestion: print w/replies, xml ) Need Help??
newperler has asked for the wisdom of the Perl Monks concerning the following question:

I have 2 fasta files with each storing DNA sequences under different individual names respectively. eg.
>John >John atgc gggg >Tom >Tom atgg ccgg ... ... (file1) (file2)
Now I need to merge the sequences from the 2 files under every same name and output as a new file. eg.
>John atgcgggg >Tom atggccgg ... (newfile)
I would like to use hash to store the names and sequences then push them into new hashes. Since I am really a newbie, so could anyone tell me how to merge the values of 2 hashes? thanks a lot!

Replies are listed 'Best First'.
Re: how to merge the files of DNA sequences?
by beable (Friar) on Jul 24, 2004 at 08:09 UTC
    Please read this documentation to help you learn: perlfunc, perlretut, perlreftut, perlre.
    #!/usr/bin/perl use strict; use warnings; my %sequences; # read the input files, passing in a filename and # a reference to the sequences hash read_file("file1", \%sequences); read_file("file2", \%sequences); # write the output file, passing in a filename and # a reference to the sequences hash write_file("file3", \%sequences); sub read_file { my $filename = shift; my $seqref = shift; open SEQFILE, "<$filename" or die "can't open $filename: $!"; # use greater-than for record separator # see perldoc perlvar local $/ = ">"; while(my $line = <SEQFILE>) { # the data will match a word, followed by a # newline, followed by another word # see perldoc perlretut and perlre if ($line =~ m/(\w+)\n(\w+)/s) { # the first word captured is the name my $name = $1; # the second word captured is the sequence my $sequence = $2; # add the sequence on to what ever is # already there $seqref->{$name} .= $sequence; } } close SEQFILE; } sub write_file { my $filename = shift; my $seqref = shift; open OUTPUT, ">$filename" or die "can't open $filename: $!"; # write the sequences hash to the output file for my $key (sort keys %{$seqref}) { print OUTPUT ">$key\n$seqref->{$key}\n" or die "can't write: $!"; } close OUTPUT or die "can't close $filename: $!"; } __END__
Re: how to merge the files of DNA sequences?
by stajich (Chaplain) on Jul 24, 2004 at 13:20 UTC
    use strict; use Bio::SeqIO; use Bio::Seq; my %seqs; my @files = qw(file1 file2); for my $file ( @files ) { my $in = Bio::SeqIO->new(-format => 'fasta', -file => $file); while( my $seq = $in->next_seq ) { $seqs{$seq->display_id} .= $seq->seq; # append the seqdata } } my $out = Bio::SeqIO->new(-format => 'fasta', -file => '>newfile.fa'); while( my ($seqname,$seqstr) = each %seqs ) { my $seq = Bio::Seq->new(-id => $seqname, -seq => $seqstr); $out->write_seq($seq); }
    Of course if you wanted to have sequence data in another file format you just have to change the 'fasta' to something else like 'genbank', 'swiss', 'embl', etc...
Re: how to merge the files of DNA sequences?
by wfsp (Abbot) on Jul 24, 2004 at 08:58 UTC
    This is what I came up with:
    #!/bin/perl5 use strict; use warnings; @ARGV = qw( file1.txt file2.txt ); my $name; my %hash; while (<>){ chomp; my $record = $_; if ( $record =~ /^>/ ){ $name = $record; next; } else{ $hash{$name} .= $record } } for my $key ( keys %hash ){ print "$key\n$hash{$key}\n" }
    Updated: Use hash instead of a hashref

      perl -lne '/^>(.*)/ or$H{$1}.=$_;END{print for map{">$_\n$H{$_}"}keys%H}' file1.txt file2.txt

        Ok, ok I'm impressed! I'm still at the 'baby idiom' stage.

        ...and anyway, I like typing!

Re: how to merge the files of DNA sequences?
by DigitalKitty (Parson) on Jul 24, 2004 at 19:11 UTC
    Hi newperler.

    I felt as though you might enjoy these two books:

    • Title: Learning Perl (3rd edition)
    • ISBN: 0596001320
    • List Price: $34.95

    • Title: Beginning Perl for Bioinformatics
    • ISBN: 0596000804
    • List Price: $39.95

    and the following additional site:

    Hope this helps,
Re: how to merge the files of DNA sequences?
by graff (Chancellor) on Jul 24, 2004 at 19:50 UTC
    Are you confident that the two files have the same number of lines, the same number and set of individual names, and the same number of sequences per individual? And, are the individuals presented in the same order? That is, are the two files already aligned?

    If there is a lack of alignment between the two, then some more specification is needed about what to do to reconcile differences between the two files.

    But if the files are fully aligned, you could use a trivial perl script to join the two files line-by-line (or use the time-honored "paste" utility that has been in /usr/bin/ on unix systems since forever):

    #!/usr/bin/perl open( F1, "file1" ) or die "file1: $!"; open( F2, "file2" ) or die "file2: $!"; while ( $s1 = <F1> ) { $s2 = <F2>; if ( $s1 =~ /^>/ ) { print $s1; } else { chomp $s1; print "$s1$s2"; # (update: added "$" on "s1") } }
    or, using the "join" command and an even shorter perl script (which just removes duplicated individual names):
    paste -d '' file1 file2 | perl -pe 's/(?<=\w)>.*//' > files.joined
    (updates: mistakenly started with "join" command instead of "paste"; added the "-d ''" option on the paste command, to concatentate input strings with no separator. Regarding the (?<=\w)>.*, see the perlre man page about "zero-width look-behind assertion" -- this RE is checking for an angle bracket preceded by an alphanumeric, and replacing that angle bracket, and everything after it on the line, with an empty string. If a name ends in something other than a letter or digit, this will fail to remove the duplication.)

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