Bio::Assembly ContigAnalysis
SummaryIncluded librariesPackage variablesSynopsisDescriptionGeneral documentationMethods
Toolbar
WebCvs
Summary
Bio::Assembly::ContigAnalysis -
Perform analysis on sequence assembly contigs.
Package variables
No package variables defined.
Inherit
Bio::Root::Root
Synopsis
    # Module loading
use Bio::Assembly::ContigAnalysis;
# Assembly loading methods my $ca = Bio::Assembly::ContigAnalysis->new( -contig=>$contigOBJ ); my @lcq = $ca->low_consensus_quality; my @hqd = $ca->high_quality_discrepancies; my @ss = $ca->single_strand_regions;
Description
A contig is as a set of sequences, locally aligned to each other, when
the sequences in a pair may be aligned. It may also include a
consensus sequence. Bio::Assembly::ContigAnalysis is a module
holding a collection of methods to analyze contig objects. It was
developed around the Bio::Assembly::Contig implementation of contigs and
can not work with another contig interface.
Methods
newDescriptionCode
high_quality_discrepanciesDescriptionCode
low_consensus_qualityDescriptionCode
not_confirmed_on_both_strandsDescriptionCode
single_strandDescriptionCode
_merge_overlapping_featuresDescriptionCode
_complementary_features_listDescriptionCode
Methods description
newcode    nextTop
 Title     : new
Usage : my $contig = Bio::Assembly::ContigAnalysis->new(-contig=>$contigOBJ);
Function : Creates a new contig analysis object
Returns : Bio::Assembly::ContigAnalysis
Args :
-contig : a Bio::Assembly::Contig object
high_quality_discrepanciescodeprevnextTop
 Title     : high_quality_discrepancies
Usage : my $sfc = $ContigAnal->high_quality_discrepancies();
Function :
Locates all high quality discrepancies among aligned sequences and the consensus sequence. Note: see Bio::Assembly::Contig POD documentation, section "Coordinate System", for a definition of available types. Default coordinate system type is "gapped consensus", i.e. consensus sequence (with gaps) coordinates. If limits are not specified, the entire alignment is analyzed. Returns : Bio::SeqFeature::Collection Args : optional arguments are -threshold : cutoff value for low quality (minimum high quality) Default: 40 -ignore : number of bases that will not be analysed at both ends of contig aligned elements Default: 5 -start : start of interval that will be analyzed -end : start of interval that will be analyzed -type : coordinate system type for interval
low_consensus_qualitycodeprevnextTop
 Title     : low_consensus_quality
Usage : my $sfc = $ContigAnal->low_consensus_quality();
Function : Locates all low quality regions in the consensus
Returns : an array of Bio::SeqFeature::Generic objects
Args : optional arguments are
-threshold : cutoff value for low quality (minimum high quality)
Default: 25
-start : start of interval that will be analyzed
-end : start of interval that will be analyzed
-type : coordinate system type for interval
not_confirmed_on_both_strandscodeprevnextTop
 Title     : low_quality_consensus
Usage : my $sfc = $ContigAnal->low_quality_consensus();
Function :
Locates all regions whose consensus bases were not confirmed by bases from sequences aligned in both orientations, i.e., in such regions, no bases in aligned sequences of either +1 or -1 strand agree with the consensus bases. Returns : an array of Bio::SeqFeature::Generic objects Args : optional arguments are -start : start of interval that will be analyzed -end : start of interval that will be analyzed -type : coordinate system type for interval
single_strandcodeprevnextTop
 Title     : single_strand
Usage : my $sfc = $ContigAnal->single_strand();
Function :
Locates all regions covered by aligned sequences only in one of the two strands, i.e., regions for which aligned sequence's strand() method returns +1 or -1 for all sequences. Returns : an array of Bio::SeqFeature::Generic objects Args : optional arguments are -start : start of interval that will be analyzed -end : start of interval that will be analyzed -type : coordinate system type for interval
_merge_overlapping_featurescodeprevnextTop
 Title     : _merge_overlapping_features
Usage : my @feat = $ContigAnal->_merge_overlapping_features(@features);
Function : Merge all overlapping features into features
that hold original features as sub-features
Returns : array of Bio::SeqFeature::Generic objects
Args : array of Bio::SeqFeature::Generic objects
_complementary_features_listcodeprevnextTop
 Title     : _complementary_features_list
Usage : @feat = $ContigAnal->_complementary_features_list($start,$end,@features);
Function : Build a list of features for regions
not covered by features in @features array
Returns : array of Bio::SeqFeature::Generic objects
Args :
$start : [integer] start of first output feature
$end : [integer] end of last output feature
@features : array of Bio::SeqFeature::Generic objects
Methods code
newdescriptionprevnextTop
sub new {
    my($class,@args) = @_;
    my $self = $class->SUPER::new(@args);

    my ($contigOBJ) = $self->_rearrange([qw(CONTIG)],@args);
    unless ($contigOBJ->isa("Bio::Assembly::Contig")) {
	$self->throw("ContigAnal works only on Bio::Assembly::Contig objects\n");
    }

    $self->{'_objref'} = $contigOBJ;
    return $self;
}
high_quality_discrepanciesdescriptionprevnextTop
sub high_quality_discrepancies {
    my ($self,@args) = shift; # Package reference
my ($threshold,$ignore,$start,$end,$type) = $self->_rearrange([qw(THRESHOLD IGNORE START END TYPE)],@args); # Defining default threhold and HQD_ignore
$threshold = 40 unless (defined($threshold)); $ignore = 5 unless (defined($ignore)); $type = 'gapped consensus' unless (defined($type)); # Changing input coordinates system (if needed)
if (defined $start && $type ne 'gapped consensus') { $start = $self->{'_objref'}->change_coord($type,'gapped consensus',$start); } elsif (!defined $start) { $start = 1; } if (defined $end && $type ne 'gapped consensus') { $end = $self->{'_objref'}->change_coord($type,'gapped consensus',$end); } elsif (!defined $end) { $end = $self->{'_objref'}->get_consensus_length(); } # Scanning each read sequence and the contig sequence and
# adding discrepancies to Bio::SeqFeature::Collection
my @seqIDs = $self->{'_objref'}->get_seq_ids(-start=>$start, -end=>$end, -type=>$type); my $consensus = $self->{'_objref'}->get_consensus_sequence()->seq; my @HQD = (); foreach my $seqID (@seqIDs) { # Setting aligned read sub-sequence limits and loading data
my $seq = $self->{'_objref'}->get_seq_by_name($seqID); my $qual = $self->{'_objref'}->get_qual_by_name($seqID); unless (defined $qual) { $self->warn("Can't correctly evaluate HQD without aligned sequence qualities for $seqID"); next; } my $sequence = $seq->seq; my @quality = @{ $qual->qual }; # Scanning the aligned region of each read
my $seq_ix = 0; my $coord = $self->{'_objref'}->get_seq_feat_by_tag($seq,"_align_clipping:$seqID"); if (!$coord) { $self->warn("Read $seqID has no alignment coordinates; considered low quality.\nSkipping..."); next; } my ($astart,$aend) = ($coord->start,$coord->end); $astart = $astart + $ignore; # Redefining limits to evaluate HQDs (jump $ignore at start)
$aend = $aend - $ignore; # Redefining limits to evaluate HQDs (stop $ignore before end)
my ($d_start,$d_end,$i); for ($i=$astart-1; $i<=$aend-1; $i++) { # Changing coordinate $i+1 from 'gapped consensus' mode to "aligned $seqID" (coordinate $seq_ix)
$seq_ix = $self->{'_objref'}->change_coord('gapped consensus',"aligned $seqID",$i+1); next unless (($i >= $start) && ($i <= $end)); my $r_base = uc(substr($sequence,$seq_ix-1,1)); my $c_base = uc(substr($consensus,$i,1)); # Discrepant region start: store $d_start and $type
(!defined($d_start) && ($r_base ne $c_base) && ($quality[$seq_ix-1] >= $threshold)) && do { $d_start = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i+1); #print $seqID," ",$r_base," ",$i+1," ",$c_base," ",$contig_ix-1," ",$quality[$i]," $type\n";
next; }; # Quality change or end of discrepant region: store limits and undef $d_start
if (defined($d_start) && (($quality[$seq_ix-1] < $threshold) || (uc($r_base) eq uc($c_base)))) { $d_end = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i); #print $seqID," ",$r_base," ",$i+1," ",$c_base," ",$contig_ix-1," ",$quality[$i]," $type\n";
push(@HQD, Bio::SeqFeature::Generic->new(-primary=>"high_quality_discrepancy:$seqID", -start=>$d_start, -end=>$d_end, -strand=>$seq->strand()) ); $d_start = undef; next; } } # for ($i=$astart-1; $i<=$aend-1; $i++)
# Loading discrepancies located at sub-sequence end, if any.
if (defined($d_start)) { $d_end = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i); push(@HQD, Bio::SeqFeature::Generic->new(-primary=>"high_quality_discrepancy:$seqID", -start=>$d_start, -end=>$d_end, -strand=>$seq->strand()) ); } } # foreach my $seqID (@seqIDs)
return @HQD;
}
low_consensus_qualitydescriptionprevnextTop
sub low_consensus_quality {
    my ($self,@args) = shift; # Packege reference
my ($threshold,$start,$end,$type) = $self->_rearrange([qw(THRESHOLD START END TYPE)],@args); # Setting default value for threshold
$threshold = 25 unless (defined($threshold)); # Loading qualities
my @quality = @{ $self->{'_objref'}->get_consensus_quality()->qual }; # Changing coordinates to gap mode noaln (consed: consensus without alignments)
$start = 1 unless (defined($start)); if (defined $start && defined $type && ($type ne 'gapped consensus')) { $start = $self->{'objref'}->change_coord($type,'gapped consensus',$start); $end = $self->{'objref'}->change_coord($type,'gapped consensus',$end) if (defined($end)); } $end = $self->{'_objref'}->get_consensus_length unless (defined $end); # Scanning @quality vector and storing intervals limits with base qualities less then
# the threshold value
my ($lcq_start); my ($i,@LCQ); for ($i=$start-1; $i<=$end-1; $i++) { # print $quality[$i],"\t",$i,"\n";
if (!defined($lcq_start) && (($quality[$i] <= $threshold) || ($quality[$i] == 98))) { $lcq_start = $i+1; } elsif (defined($lcq_start) && ($quality[$i] > $threshold)) { $lcq_start = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$lcq_start); my $lcq_end = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i); push(@LCQ, Bio::SeqFeature::Generic->new(-start=>$lcq_start, -end=>$lcq_end, -primary=>'low_consensus_quality') ); $lcq_start = undef; } } if (defined $lcq_start) { $lcq_start = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$lcq_start); my $lcq_end = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i); push(@LCQ, Bio::SeqFeature::Generic->new(-start=>$lcq_start, -end=>$lcq_end, -primary=>'low_consensus_quality') ); } return @LCQ;
}
not_confirmed_on_both_strandsdescriptionprevnextTop
sub not_confirmed_on_both_strands {
    my ($self,@args) = shift; # Package reference
my ($start,$end,$type) = $self->_rearrange([qw(START END TYPE)],@args); # Changing coordinates to default system 'align' (contig sequence with alignments)
$start = 1 unless (defined($start)); if (defined($type) && ($type ne 'gapped consensus')) { $start = $self->{'_objref'}->change_coord($type,'gapped consensus',$start); $end = $self->{'_objref'}->change_coord($type,'gapped consensus',$end) if (defined($end)); } $end = $self->{'_objref'}->get_consensus_length unless (defined($end)); # Scanning alignment
my %confirmed = (); # If ($confirmed{$orientation}[$i] > 0) then $i is confirmed in $orientation strand
my ($i); my $consensus = $self->{'_objref'}->get_consensus_sequence()->seq; foreach my $seqID ($self->{'_objref'}->get_seq_ids) { # Setting aligned read sub-sequence limits and loading data
my $seq = $self->{'_objref'}->get_seq_by_name($seqID); my $sequence = $seq->seq; # Scanning the aligned regions of each read and registering confirmed sites
my $contig_ix = 0; my $coord = $self->{'_objref'}->get_seq_feat_by_tag($seq,"_align_clipping:$seqID"); my ($astart,$aend,$orientation) = ($coord->start,$coord->end,$coord->strand); $astart = $self->{'_objref'}->change_coord('gapped consensus',"aligned $seqID",$astart); $aend = $self->{'_objref'}->change_coord('gapped consensus',"aligned $seqID",$aend); for ($i=$astart-1; $i<=$aend-1; $i++) { # $i+1 in 'align' mode is $contig_ix
$contig_ix = $self->{'_objref'}->change_coord("aligned $seqID",'gapped consensus',$i+1); next unless (($contig_ix >= $start) && ($contig_ix <= $end)); my $r_base = uc(substr($sequence,$i,1)); my $c_base = uc(substr($consensus,$contig_ix-1,1)); if ($c_base eq '-') { $confirmed{$orientation}[$contig_ix] = -1; } elsif (uc($r_base) eq uc($c_base)) { # Non discrepant region found
$confirmed{$orientation}[$contig_ix]++; } } # for ($i=$astart-1; $i<=$aend-1; $i++)
} # foreach $seqID (@reads)
# Locating non-confirmed aligned regions for each orientation in $confirmed registry
my ($orientation); my @NCBS = (); foreach $orientation (keys %confirmed) { my ($ncbs_start,$ncbs_end); for ($i=$start; $i<=$end; $i++) { if (!defined($ncbs_start) && (!defined($confirmed{$orientation}[$i]) || ($confirmed{$orientation}[$i] == 0))) { $ncbs_start = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i); } elsif (defined($ncbs_start) && defined($confirmed{$orientation}[$i]) && ($confirmed{$orientation}[$i] > 0)) { $ncbs_end = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$i-1); push(@NCBS, Bio::SeqFeature::Generic->new(-start=>$ncbs_start, -end=>$ncbs_end, -strand=>$orientation, -primary=>"not_confirmed_on_both_strands") ); $ncbs_start = undef; } } if (defined($ncbs_start)) { # NCBS at the end of contig
$ncbs_end = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$end); push(@NCBS, Bio::SeqFeature::Generic->new(-start=>$ncbs_start, -end=>$ncbs_end, -strand=>$orientation, -primary=>'not_confirmed_on_both_strands') ); } } return @NCBS;
}
single_stranddescriptionprevnextTop
sub single_strand {
    my ($self,@args) = shift; # Package reference
my ($start,$end,$type) = $self->_rearrange([qw(START END TYPE)],@args); # Changing coordinates to gap mode align (consed: consensus sequence with alignments)
$type = 'gapped consensus' unless(defined($type)); $start = 1 unless (defined($start)); if (defined($type) && $type ne 'gapped consensus') { $start = $self->{'objref'}->change_coord($type,'gapped consensus',$start); $end = $self->{'objref'}->change_coord($type,'gapped consensus',$end) if (defined($end)); } ($end) = $self->{'_objref'}->get_consensus_length unless (defined($end)); # Loading complete list of coordinates for aligned sequences
my $sfc = $self->{'_objref'}->get_features_collection(); my @forward = grep { $_->primary_tag =~ /^_aligned_coord:/ } $sfc->features_in_range(-start=>$start, -end=>$end, -contain=>0, -strand=>1, -strandmatch=>'strong'); my @reverse = grep { $_->primary_tag =~ /^_aligned_coord:/ } $sfc->features_in_range(-start=>$start, -end=>$end, -contain=>0, -strand=>-1, -strandmatch=>'strong'); # Merging overlapping features
@forward = $self->_merge_overlapping_features(@forward); @reverse = $self->_merge_overlapping_features(@reverse); # Finding single stranded regions
my ($length) = $self->{'_objref'}->get_consensus_length; $length = $self->{'_objref'}->change_coord('gapped consensus','ungapped consensus',$length); @forward = $self->_complementary_features_list(1,$length,@forward); @reverse = $self->_complementary_features_list(1,$length,@reverse); my @SS = (); foreach my $feat (@forward, @reverse) { $feat->primary_tag('single_strand_region'); push(@SS,$feat); } return @SS;
}
_merge_overlapping_featuresdescriptionprevnextTop
sub _merge_overlapping_features {
    my ($self,@feat) = @_;

    $self->throw_not_implemented();
}
_complementary_features_listdescriptionprevnextTop
sub _complementary_features_list {
    my ($self,$start,$end,@feat) = @_;

    $self->throw_not_implemented();
}

1;

__END__
}
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 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
Support Top
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/
AUTHOR - Robson Francisco de SouzaTop
Email: rfsouza@citri.iq.usp.br
APPENDIXTop
The rest of the documentation details each of the object
methods. Internal methods are usually preceded with a _
Object creatorTop
Analysis methodsTop
Internal MethodsTop