Bio::SeqIO fastq
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Summary
Bio::SeqIO::fastq - fastq sequence input/output stream
Package variables
No package variables defined.
Included modules
Bio::Seq::SeqFactory
Inherit
Bio::SeqIO
Synopsis
  ################## pertains to FASTQ parsing only ##################
# grabs the FASTQ parser, specifies the Illumina variant my $in = Bio::SeqIO->new(-format => 'fastq-illumina', -file => 'mydata.fq'); # simple 'fastq' format defaults to 'sanger' variant my $out = Bio::SeqIO->new(-format => 'fastq', -file => '>mydata.fq'); # $seq is a Bio::Seq::Quality object while (my $seq = $in->next_seq) { $out->write_seq($seq); # convert Illumina 1.3 to Sanger format } # for 4x faster parsing, one can do something like this for raw data use Bio::Seq::Quality; # $data is a hash reference containing all arguments to be passed to # the Bio::Seq::Quality constructor while (my $data = $in->next_dataset) { # process $data, such as trim, etc my $seq = Bio::Seq::Quality->new(%$data); # for now, write_seq only accepts Bio::Seq::Quality, but may be modified # to allow raw hash references for speed $out->write_seq($data); }
Description
This object can transform Bio::Seq and Bio::Seq::Quality objects to and from
FASTQ flat file databases.
FASTQ is a file format used frequently at the Sanger Centre and in next-gen
sequencing to bundle a FASTA sequence and its quality data. A typical FASTQ
entry takes the form:
  @HCDPQ1D0501
GATTTGGGGTTCAAAGCAGTATCGATCAAATAGTAAATCCATTTGTTCAACTCACAGTTT.....
+HCDPQ1D0501
!''*((((***+))%%%++)(%%%%).1***-+*''))**55CCF>>>>>>CCCCCCC65.....
where:
  @ = descriptor, followed by one or more sequence lines
+ = optional descriptor (if present, must match first one), followed by one or
more qual lines
When writing FASTQ output the redundant descriptor following the '+' is by
default left off to save disk space. If needed, one can set the quality_header()
flag in order for this to be printed. FASTQ files have sequence and quality data on single line or multiple lines, and
the quality values are single-byte encoded. Data are mapped very simply to
Bio::Seq::Quality instances:
    Data                                        Bio::Seq::Quality method
------------------------------------------------------------------------
first non-whitespace chars in descriptor id^
descriptor line desc^
sequence lines seq
quality qual*
FASTQ variant namespace
^ first nonwhitespace chars are id(), everything else after (to end of line) is in desc() * Converted to PHRED quality scores where applicable ('solexa')
This parser supports all variants of FASTQ, including Illumina v 1.0 and 1.3:
    variant                note
-----------------------------------------------------------
sanger original
solexa Solexa, Inc. (2004), aka Illumina 1.0
illumina Illumina 1.3
The variant can be specified by passing by either passing the additional
-variant parameter to the constructor:
  my $in = Bio::SeqIO->new(-format    => 'fastq',
-variant => 'solexa',
-file => 'mysol.fq');
or by passing the format and variant together (Bio::SeqIO will now handle
this and convert it accordingly to the proper argument):
  my $in = Bio::SeqIO->new(-format    => 'fastq-solexa',
-file => 'mysol.fq');
Variants can be converted back and forth from one another; however, due to
the difference in scaling for solexa quality reads, converting from 'illumina'
or 'sanger' FASTQ to solexa is not recommended.
Methods
_initialize
No description
Code
next_seqDescriptionCode
next_datasetDescriptionCode
write_seqDescriptionCode
write_fastqDescriptionCode
write_fastaDescriptionCode
write_qualDescriptionCode
_init_tables
No description
Code
validateDescriptionCode
quality_headerDescriptionCode
Methods description
next_seqcode    nextTop
 Title    : next_seq
Usage : $seq = $stream->next_seq()
Function : returns the next sequence in the stream
Returns : Bio::Seq::Quality object
Args : NONE
Status : Stable
next_datasetcodeprevnextTop
 Title    : next_dataset
Usage : $obj->next_dataset
Function : returns a hash reference containing the parsed data
Returns : hash reference
Args : none
Status : Stable
write_seqcodeprevnextTop
 Title    : write_seq
Usage : $stream->write_seq(@seq)
Function : writes the $seq object into the stream
Returns : 1 for success and 0 for error
Args : Bio::Seq::Quality
Note : This now conforms to SeqIO spec (module output is same format as
next_seq)
Status : Stable
write_fastqcodeprevnextTop
 Title   : write_fastq
Usage : $stream->write_fastq(@seq)
Function: writes the $seq object into the stream
Returns : 1 for success and 0 for error
Args : Bio::Seq::Quality object
Status : Deprecated (delegates to write_seq)
write_fastacodeprevnextTop
 Title   : write_fasta
Usage : $stream->write_fasta(@seq)
Function: writes the $seq object into the stream
Returns : 1 for success and 0 for error
Args : Bio::Seq object
Note : This method does not currently delegate to Bio::SeqIO::fasta
(maybe it should?). Not sure whether we should keep this as a
convenience method.
Status : Unstable
write_qualcodeprevnextTop
 Title   : write_qual
Usage : $stream->write_qual(@seq)
Function: writes the $seq object into the stream
Returns : 1 for success and 0 for error
Args : Bio::Seq::Quality object
Note : This method does not currently delegate to Bio::SeqIO::qual
(maybe it should?). Not sure whether we should keep this as a
convenience method.
Status : Unstable
validatecodeprevnextTop
 Title    : validate
Usage : $obj->validate(0)
Function : flag for format/qual range validation - default is 1, validate
Returns : Bool (0/1)
Args : Bool (0/1)
Status : Stable (may be moved to interface)
quality_headercodeprevnextTop
 Title    : quality_header
Usage : $obj->quality_header
Function : flag for printing quality header - default is 0, no header
Returns : Bool (0/1)
Args : Bool (0/1)
Status : Unstable (name may change dep. on feedback)
Methods code
_initializedescriptionprevnextTop
sub _initialize {
    my($self,@args) = @_;
    $self->SUPER::_initialize(@args);
    my ($variant, $validate, $header) = $self->_rearrange([qw(VARIANT
                                                              VALIDATE
                                                              QUALITY_HEADER)], @args);
    $variant ||= 'sanger';
    $self->variant($variant);
    $self->_init_tables($variant);
    $validate = defined $validate ? $validate : 1;
    $self->validate($validate);
    $header     && $self->quality_header($header);

    if( ! defined $self->sequence_factory ) {
        $self->sequence_factory(Bio::Seq::SeqFactory->new(
            -verbose => $self->verbose(),
            -type => 'Bio::Seq::Quality')
        );
    }
}
next_seqdescriptionprevnextTop
sub next_seq {
    my( $self ) = @_;
    while (defined(my $data = $self->next_dataset)) {
        # Are FASTQ sequences w/o any sequence valid?  Removing for now
# -cjfields 6.22.09
my $seq = $self->sequence_factory->create(%$data); return $seq; } return; } # pure perl version
}
next_datasetdescriptionprevnextTop
sub next_dataset {
    my $self = shift;
    local $/ = "\n";
    my $data;
    my $mode = '-seq';
    # speed this up by directly accessing the filehandle and in-lining the
# _readline stuff vs. making the repeated method calls. Tradeoff is speed
# over repeated code.
# we can probably normalize line endings using PerlIO::eol or
# Encode::Newlines
my $fh = $self->_fh; my $line = $self->{lastline} || <$fh>; FASTQ: while (defined $line) { $line =~ s/\015\012/\012/; $line =~ tr/\015/\n/; if ($mode eq '-seq' && $line =~ m{^@([^\n]+)$}xmso) { $data->{-descriptor} = $1; my ($id,$fulldesc); if ($data->{-descriptor} =~ /^\s*(\S+)\s*(.*)/) { ($id,$fulldesc) = ($1, $2); } else { $self->throw("Can't parse fastq header"); } $data->{-id} = $id; $data->{-desc} = $fulldesc; $data->{-namespace} = $self->variant; } elsif ($mode eq '-seq' && $line =~ m{^\+([^\n]*)}xmso) { my $desc = $1; $self->throw("No description line parsed") unless $data->{-descriptor}; if ($desc && $data->{-descriptor} ne $desc) { $self->throw("Quality descriptor [$desc] doesn't match seq ". "descriptor ".$data->{-descriptor}.", line: $." ); } $mode = '-raw_quality'; } else { if ($mode eq '-raw_quality' && defined($data->{-raw_quality}) && (length($data->{-raw_quality}) >= length($data->{-seq}))) { $self->{lastline} = $line; last FASTQ } chomp $line; if ($line =~ /^$/) { delete $self->{lastline}; last FASTQ; } $data->{$mode} .= $line } $line = <$fh>; if (!defined $line) { delete $self->{lastline}; last FASTQ; } } return unless $data; if (!$data->{-seq} || !defined($data->{-raw_quality})) { $self->throw("Missing sequence and/or quality data; line: $."); } # simple quality control tests
if (length $data->{-seq} != length $data->{-raw_quality}) { $self->throw("Quality string [".$data->{-raw_quality}."] of length [". length($data->{-raw_quality})."]\ndoesn't match length of sequence ". $data->{-seq}."\n[".length($data->{-seq})."], line: $."); } $data->{-qual} = [map { if ($self->{_validate_qual} && !exists($self->{chr2qual}->{$_})) { $self->throw("Unknown symbol with ASCII value ".ord($_)." outside ". "of quality range") # TODO: fallback?
} $self->variant eq 'solexa' ? $self->{sol2phred}->{$self->{chr2qual}->{$_}}: $self->{chr2qual}->{$_}; } unpack("A1" x length($data->{-raw_quality}), $data->{-raw_quality})]; return $data; } # This should be creating fastq output only. Bio::SeqIO::fasta and
# Bio::SeqIO::qual should be used for that output
}
write_seqdescriptionprevnextTop
sub write_seq {
    my ($self,@seq) = @_;
    my $var = $self->variant;
    foreach my $seq (@seq) {
        unless ($seq->isa("Bio::Seq::Quality")){
            $self->warn("You can't write FASTQ without supplying a Bio::Seq::".
                "Quality object! ".ref($seq)."\n");
            next;
        }
        my $str = $seq->seq || '';
        my @qual = @{$seq->qual};

        # this should be the origin of the sequence (illumina, solexa, sanger)
my $ns= $seq->namespace; my $top = $seq->display_id(); if (my $desc = $seq->desc()) { $desc =~ s/\n//g; $top .= " $desc"; } my $qual = ''; my $qual_map = ($ns eq 'solexa' && $var eq 'solexa') ? $self->{phred_fp2chr} : ($var eq 'solexa') ? $self->{phred_int2chr} : $self->{qual2chr}; my %bad_qual; for my $q (@qual) { $q = sprintf("%.0f", $q) if ($var ne 'solexa' && $ns eq 'solexa'); if (exists $qual_map->{$q}) { $qual .= $qual_map->{$q}; next; } else { # fuzzy mapping, for edited qual scores
my $qr = sprintf("%.0f",$q); my $bounds = sprintf("%.1f-%.1f",$qr-0.5, $qr+0.5); if (exists $self->{fuzzy_qual2chr}->{$bounds}) { $qual .= $self->{fuzzy_qual2chr}->{$bounds}; next; } else { my $rep = ($q <= $self->{qual_start}) ? $qual_map->{$self->{qual_start}} : $qual_map->{$self->{qual_end}}; $qual .= $rep; $bad_qual{$q}++; } } } if ($self->{_validate_qual} && %bad_qual) { $self->warn("Data loss for $var: following values not found\n". join(',',sort {$a <=> $b} keys %bad_qual)) } $self->_print("\@",$top,"\n",$str,"\n") or return; $self->_print("+",($self->{_quality_header} ? $top : ''),"\n",$qual,"\n") or return; } return 1;
}
write_fastqdescriptionprevnextTop
sub write_fastq {
    my ($self,@seq) = @_;
    return $self->write_seq(@seq);
}
write_fastadescriptionprevnextTop
sub write_fasta {
    my ($self,@seq) = @_;
    if (!exists($self->{fasta_proxy})) {
        $self->{fasta_proxy} = Bio::SeqIO->new(-format => 'fasta', -fh => $self->_fh);
    }
    return $self->{fasta_proxy}->write_seq(@seq);
}
write_qualdescriptionprevnextTop
sub write_qual {
    my ($self,@seq) = @_;
    if (!exists($self->{qual_proxy})) {
        $self->{qual_proxy} = Bio::SeqIO->new(-format => 'qual', -fh => $self->_fh);
    }
    return $self->{qual_proxy}->write_seq(@seq);
}

# variant() method inherited from Bio::Root::IO
}
_init_tablesdescriptionprevnextTop
sub _init_tables {
    my ($self, $var) = @_;
    # cache encode/decode values for quicker accession
($self->{qual_start}, $self->{qual_end}, $self->{qual_offset}) = @{ $variant{$var} }{qw(qual_start qual_end offset)}; if ($var eq 'solexa') { for my $q ($self->{qual_start} .. $self->{qual_end}) { my $char = chr($q + $self->{qual_offset}); $self->{chr2qual}->{$char} = $q; $self->{qual2chr}->{$q} = $char; my $s2p = 10 * log(1 + 10 ** ($q / 10.0)) / log(10); # solexa <=> solexa mapping speedup (retain floating pt precision)
$self->{phred_fp2chr}->{$s2p} = $char; $self->{sol2phred}->{$q} = $s2p; # this is for mapping values fuzzily (fallback)
$self->{fuzzy_qual2chr}->{sprintf("%.1f-%.1f",$q - 0.5, $q + 0.5)} = $char; next if $q < 0; # skip loop; PHRED scores greater than 0
my $p2s = sprintf("%.0f",($q <= 1) ? -5 : 10 * log(-1 + 10 ** ($q / 10.0)) / log(10)); # sanger/illumina PHRED <=> Solexa char mapping speedup
$self->{phred_int2chr}->{$q} = chr($p2s + $self->{qual_offset}); } } else { for my $c ($self->{qual_start}..$self->{qual_end}) { # PHRED mapping
my $char = chr($c + $self->{qual_offset}); $self->{chr2qual}->{$char} = $c; $self->{qual2chr}->{$c} = $char; # this is for mapping values not found with above
$self->{fuzzy_qual2chr}->{sprintf("%.1f-%.1f",$c - 0.5, $c + 0.5)} = $char; } }
}
validatedescriptionprevnextTop
sub validate {
    my ($self, $val) = @_;
    if (defined $val) {
        $self->{_validate_qual} = $val;
    }
    return $self->{_validate_qual};
}
quality_headerdescriptionprevnextTop
sub quality_header {
    my ($self, $val) = @_;
    if (defined $val) {
        $self->{_quality_header} = $val;
    }
    return $self->{_quality_header} || 0;
}

1;

__END__

# BioPerl module for Bio::SeqIO::fastq
#
# Please direct questions and support issues to <bioperl-l@bioperl.org>
#
# Cared for Chris Fields
#
# Completely refactored from the original FASTQ parser
# by Tony Cox <avc@sanger.ac.uk>
#
# Copyright Chris Fields
#
# You may distribute this module under the same terms as perl itself
#
# _history
#
# October 29, 2001 incept data (Tony Cox)
# June 20, 2009 updates for Illumina variant FASTQ formats for Solexa and later
# Aug 26, 2009 fixed bugs and added tests for fastq.t
# POD documentation - main docs before the code
}
General documentation
FEEDBACKTop
Mailing ListsTop
User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to one
of the Bioperl mailing lists. Your participation is much appreciated.
  bioperl-l@bioperl.org                  - General discussion
http://bioperl.org/wiki/Mailing_lists - About the mailing lists
SupportTop
Please direct usage questions or support issues to the mailing list:
bioperl-l@bioperl.org
rather than to the module maintainer directly. Many experienced and
reponsive experts will be able look at the problem and quickly
address it. Please include a thorough description of the problem
with code and data examples if at all possible.
Reporting BugsTop
Report bugs to the Bioperl bug tracking system to help us keep track
the bugs and their resolution. Bug reports can be submitted via the
web:
  https://redmine.open-bio.org/projects/bioperl/
AUTHORS - Chris Fields (taken over from Tony Cox)Top
Email: cjfields at bioperl dot org
APPENDIXTop
The rest of the documentation details each of the object
methods. Internal methods are usually preceded with a _
Bio::SeqIO interface methodsTop
variantTop
 Title   : variant
Usage : $format = $obj->variant();
Function: Get and set method for the quality sequence variant. This is
important for indicating the encoding/decoding to be used for
quality data.
Current values accepted are: 'sanger' (orginal FASTQ) ASCII encoding from 33-126, PHRED quality score from 0 to 93 'solexa' (aka illumina1.0) ASCII encoding from 59-104, SOLEXA quality score from -5 to 40 'illumina' (aka illumina1.3) ASCII encoding from 64-104, PHRED quality score from 0 to 40 (Derived from the MAQ website): For 'solexa', scores are converted to PHRED qual scores using: $Q = 10 * log(1 + 10 ** (ord($sq) - 64) / 10.0)) / log(10) Returns : string Args : new value, string
Plugin-specific methodsTop