Dear Wise Monks,
SHORT VERSION
How would you write a regex for a conditional statement that
searches for a string of the same character (N) that stretches across multiple lines and then replaces this multi -line block of Ns with something else?
LONG VERSION
I am trying to write a program that reads an input file formatted as follows:
>scaffold00001
TGACCAGCGTTACATGTCAACGTTTTTTTAAACATTGAATATTTATTCATCTGTTCTCGA
CGTCGCACATTGTGCAAGCCATCAACTTGATCTAATTAAGTATATCCGCTAAAGATCAGC
GCCTTTTGTTTTGACAACAACAAGTATCATACCAGCACTTTAACGATGTAGTCAATAAAA
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TGTCTGCTTCCGTTGATACCTGCGCGAGCCGGTCGTCACGATTCGGTACCTTGCCGTCAA
TCAAAAAATGGCAATGATGATCCAACAATGGGACTTGGTCGACAAACTCAGATAAGTCGT
CCAAAATACTTCCTCCTTCACACGTTTGCTGGTGCAATGACCAGCCCACGTTTTCCTAGA
>scaffold00002
ATTCATGTTGCTCGTCGTCACCTGACCGAGCAGGGCCAGAACCGGGACATGATCCATTTT
GGCATCATACAAACCATTTAATAGATGAATGGCGCCAGGGCCGCCAATGGAGAGACAAAC
ACCCAAACCGCCTGTTAACTTAGCAGTTGCCGCTGCGGACAAAGCGGCGACTTCCTCATG
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
CAACTGCTCTTAGTGTGATCTCATTTATCAAAGAGATCAGACTTTGTGAATTCAGATTTT
TTCAAGCCATACAACAACTAACCCAATTTAAGAAATACCCACTTATTGCGATTTGCTTTT
CTATTAGTTAGCATTTTAAATTGTGAAACGTGCCACTTATAAACAAATTTCCGTCTTCTT
The script should then replace the lines that do not contain a G, A , T or C with a string that exits only on one line.
The code I have so far is as follows:
#!/util/bin/perl
use strict;
use warnings;
use File::Copy;
#################
#-----Declaration of Arguements-----#
my $fasta=$ARGV[0] || die ("Please provide a 454Scaffolds.fna fasta fi
+le to parse.\n"); # Argument accepts scaffold fasta file.
my $tempfasta="temp.fasta";
my $workingfasta="working.fasta";
my $scaffold;
+ # Initializing $scaffold globally.
my $enumerator;
+ # Initializing $enumerator globally.
#----Main Program-----#
copy($fasta, $tempfasta) or die "Could not copy $fasta to $workingfast
+a.";
open (FILE,"<temp.fasta") || die ("Could not open fasta file!\n"); # O
+pen & read fasta file
open (WORKFILE,">>working.fasta");
while (my $fastaline=<FILE>)
{
if($fastaline=~ m/^>/)
+ # IF first character in line is > assign line to $fastaline then...
{
my $scaffold_header=$fastaline;
+ # set $scaffold_header to $fastaline then...
$scaffold_header=~ /(>)(\S*)(\s*)(\S*)/;
+ # divide $ scaffold header components then...
$scaffold= $2;
+ # assign component $2 to $scaffold then...
print WORKFILE ">" . "$scaffold" . ".1\n";
+ # print $scaffold to screen and start new line.
$enumerator=1;
} elsif ($fastaline!~ m/G/ and $fastaline!~ m/A/ and $fastaline!~ m/T
+/ and $fastaline!~ m/C/)
{
$enumerator++;
print WORKFILE (">" . "$scaffold" . ".$enumerator\n");
} else {
print WORKFILE $fastaline;
}
};
close (FILE);
close (WORKFILE);
So, the output I get with this code as is, is close to what I want but not exactly so. This is what the output looks like now:
>scaffold00001.1
TGACCAGCGTTACATGTCAACGTTTTTTTAAACATTGAATATTTATTCATCTGTTCTCGA
CGTCGCACATTGTGCAAGCCATCAACTTGATCTAATTAAGTATATCCGCTAAAGATCAGC
GCCTTTTGTTTTGACAACAACAAGTATCATACCAGCACTTTAACGATGTAGTCAATAAAA
>scaffold00001.2
>scaffold00001.3
>scaffold00001.4
TGTCTGCTTCCGTTGATACCTGCGCGAGCCGGTCGTCACGATTCGGTACCTTGCCGTCAA
TCAAAAAATGGCAATGATGATCCAACAATGGGACTTGGTCGACAAACTCAGATAAGTCGT
CCAAAATACTTCCTCCTTCACACGTTTGCTGGTGCAATGACCAGCCCACGTTTTCCTAGA
>scaffold00002.1
ATTCATGTTGCTCGTCGTCACCTGACCGAGCAGGGCCAGAACCGGGACATGATCCATTTT
GGCATCATACAAACCATTTAATAGATGAATGGCGCCAGGGCCGCCAATGGAGAGACAAAC
ACCCAAACCGCCTGTTAACTTAGCAGTTGCCGCTGCGGACAAAGCGGCGACTTCCTCATG
>scaffold00002.2
>scaffold00002.3
CAACTGCTCTTAGTGTGATCTCATTTATCAAAGAGATCAGACTTTGTGAATTCAGATTTT
TTCAAGCCATACAACAACTAACCCAATTTAAGAAATACCCACTTATTGCGATTTGCTTTT
CTATTAGTTAGCATTTTAAATTGTGAAACGTGCCACTTATAAACAAATTTCCGTCTTCTT
And this is how I WANT the output to look like:
>scaffold00001.1
TGACCAGCGTTACATGTCAACGTTTTTTTAAACATTGAATATTTATTCATCTGTTCTCGA
CGTCGCACATTGTGCAAGCCATCAACTTGATCTAATTAAGTATATCCGCTAAAGATCAGC
GCCTTTTGTTTTGACAACAACAAGTATCATACCAGCACTTTAACGATGTAGTCAATAAAA
>scaffold00001.2
TGTCTGCTTCCGTTGATACCTGCGCGAGCCGGTCGTCACGATTCGGTACCTTGCCGTCAA
TCAAAAAATGGCAATGATGATCCAACAATGGGACTTGGTCGACAAACTCAGATAAGTCGT
CCAAAATACTTCCTCCTTCACACGTTTGCTGGTGCAATGACCAGCCCACGTTTTCCTAGA
>scaffold00002.1
ATTCATGTTGCTCGTCGTCACCTGACCGAGCAGGGCCAGAACCGGGACATGATCCATTTT
GGCATCATACAAACCATTTAATAGATGAATGGCGCCAGGGCCGCCAATGGAGAGACAAAC
ACCCAAACCGCCTGTTAACTTAGCAGTTGCCGCTGCGGACAAAGCGGCGACTTCCTCATG
>scaffold00002.2
CAACTGCTCTTAGTGTGATCTCATTTATCAAAGAGATCAGACTTTGTGAATTCAGATTTT
TTCAAGCCATACAACAACTAACCCAATTTAAGAAATACCCACTTATTGCGATTTGCTTTT
CTATTAGTTAGCATTTTAAATTGTGAAACGTGCCACTTATAAACAAATTTCCGTCTTCTT
The problem is that the script is inserting the string I want to replace the Ns with for every line it sees them in, but I want it treat each consecutive line that has the string of N as a single unit.
My guess is that I need to replace the:
elsif ($fastaline!~ m/G/ and $fastaline!~ m/A/ and $fastaline!~ m/T/
+and $fastaline!~ m/C/)
With some kind of more complex regular expression. Being that I am new to regex, this is where I am stuck.
Any help would be greatly appreciated!