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NAME

Bio::Assembly::Contig - Perl module to hold and manipulate sequence assembly contigs.

SYNOPSIS

# Module loading
use Bio::Assembly::IO;

# Assembly loading methods
$aio = Bio::Assembly::IO->new(-file=>"test.ace.1",
                              -format=>'phrap');

$assembly = $aio->next_assembly;
foreach $contig ($assembly->all_contigs) {
  # do something
}

# OR, if you want to build the contig yourself,

use Bio::Assembly::Contig;
$c = Bio::Assembly::Contig->new(-id=>"1");

$ls  = Bio::LocatableSeq->new(-seq=>"ACCG-T",
                              -id=>"r1",
                              -alphabet=>'dna');
$ls2 = Bio::LocatableSeq->new(-seq=>"ACA-CG-T",
                              -id=>"r2",
                              -alphabet=>'dna');

$ls_coord = Bio::SeqFeature::Generic->new(-start=>3,
                                          -end=>8,
                                          -strand=>1);
$ls2_coord = Bio::SeqFeature::Generic->new(-start=>1,
                                           -end=>8,
                                           -strand=>1);
$c->add_seq($ls);
$c->add_seq($ls2);
$c->set_seq_coord($ls_coord,$ls);
$c->set_seq_coord($ls2_coord,$ls2);

$con = Bio::LocatableSeq->new(-seq=>"ACACCG-T",
                              -alphabet=>'dna');
$c->set_consensus_sequence($con);

$l = $c->change_coord('unaligned r2','ungapped consensus',6);
print "6 in unaligned r2 => $l in ungapped consensus\n";

DESCRIPTION

A contig is as a set of sequences, locally aligned to each other, so that every sequence has overlapping regions with at least one sequence in the contig, such that a continuous of overlapping sequences is formed, allowing the deduction of a consensus sequence which may be longer than any of the sequences from which it was deduced.

In this documentation we refer to the overlapping sequences used to build the contig as "aligned sequences" and to the sequence deduced from the overlap of aligned sequences as the "consensus". Methods to deduce the consensus sequence from aligned sequences were not yet implemented in this module, but its posssible to add a consensus sequence deduced by other means, e.g, by the assembly program used to build the alignment.

All aligned sequences in a Bio::Assembly::Contig must be Bio::Assembly::Locatable objects and have a unique ID. The unique ID restriction is due to the nature of the module's internal data structures and is also a request of some assembly programs. If two sequences with the same ID are added to a contig, the first sequence added is replaced by the second one.

Coordinate_systems

There are four base coordinate systems in Bio::Assembly::Contig. When you need to access contig elements or data that exists on a certain range or location, you may be specifying coordinates in relation to different sequences, which may be either the contig consensus or one of the aligned sequences that were used to do the assembly.

=========================================================
         Name           | Referenced sequence
---------------------------------------------------------
  "gapped consensus"    | Contig (with gaps)
  "ungapped consensus"  | Contig (without gaps)
  "aligned $seqID"      | sequence $seqID (with gaps)
  "unaligned $seqID"    | sequence $seqID (without gaps)
=========================================================

"gapped consensus" refers to positions in the aligned consensus sequence, which is the consensus sequence including the gaps inserted to align it agains the aligned sequences that were used to assemble the contig. So, its limits are [ 1, (consensus length + number of gaps in consensus) ]

"ungapped consensus" is a coordinate system based on the consensus sequence, but excluding consensus gaps. This is just the coordinate system that you have when considering the consensus sequence alone, instead of aligned to other sequences.

"aligned $seqID" refers to locations in the sequence $seqID after alignment of $seqID against the consensus sequence (reverse complementing the original sequence, if needed). Coordinate 1 in "aligned $seqID" is equivalent to the start location (first base) of $seqID in the consensus sequence, just like if the aligned sequence $seqID was a feature of the consensus sequence.

"unaligned $seqID" is equivalent to a location in the isolated sequence, just like you would have when considering the sequence alone, out of an alignment. When changing coordinates from "aligned $seq2" to "unaligned $seq2", if $seq2 was reverse complemented when included in the alignment, the output coordinates will be reversed to fit that fact, i.e. 1 will be changed to length($seq2), 2 will be length($seq)-1 and so on.

An important note: when you change gap coordinates from a gapped system ("gapped consensus" or "aligned $seqID") to a system that does not include gaps ("ungapped consensus" or "unaligned $seqID"), the position returned will be the first location before all gaps neighboring the input location.

Feature_collection

Bio::Assembly::Contig stores much information about a contig in a Bio::Assembly::SeqFeature::Collection object. Relevant information on the alignment is accessed by selecting features based on their primary tags (e.g. all features which have a primary tag of the form '_aligned_coord:$seqID', where $seqID is an aligned sequence ID, are coordinates for sequences in the contig alignment) and, by using methods from Bio::Assembly::SeqFeature::Collection, it's possible to select features by overlap with other features.

We suggest that you use the primary tags of features as identifiers for feature classes. By convention, features with primary tags starting with a '_' are generated by modules that populate the contig data structure and return the contig object, maybe as part of an assembly object, e.g. drivers from the Bio::Assembly::IO set.

Features in the features collection may be associated with particular aligned sequences. To obtain this, you must attach the sequence to the feature, using attach() seq from Bio::Assembly::SeqFeatureI, before you add the feature to the feature collection. We also suggest to add the sequence id to the primary tag, so that is easy to select feature for a particular sequence.

There is only one feature class that some methods in Bio::Assembly::Contig expect to find in the feature collection: features with primary tags of the form '_aligned_coord:$seqID', where $seqID is the aligned sequence id (like returned by $seq->id()). These features describe the position (in "gapped consensus" coordinates) of aligned sequences, and the method set_seq_coord() automatically changes a feature's primary tag to this form whenever the feature is added to the collection by this method. Only two methods in Bio::Assembly::Contig will not work unless there are features from this class: change_coord() and get_seq_coord().

Other feature classes will be automatically available only when Bio::Assembly::Contig objects are created by a specific module. Such feature classes are (or should be) documented in the documentation of the module which create them, to which the user should refer.

FEEDBACK

Mailing Lists

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

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 Bugs

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://github.com/bioperl/bioperl-live/issues

AUTHOR - Robson Francisco de Souza

rfsouza@citri.iq.usp.br

APPENDIX

The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _

Object creator

new

Title     : new
Usage     : my $contig = Bio::Assembly::Contig->new();
Function  : Creates a new contig object
Returns   : Bio::Assembly::Contig
Args      : -id         => unique contig ID
            -source     => string for the sequence assembly program used
            -collection => Bio::SeqFeature::CollectionI instance

Assembly related methods

These methods exist to enable adding information about possible relations among contigs, e.g. when you already have a scaffold for your assembly, describing the ordering of contigs in the final assembly, but no sequences covering the gaps between neighboring contigs.

source

Title     : source
Usage     : $contig->source($program);
Function  : Get/Set program used to build this contig
Returns   : string
Argument  : [optional] string

assembly

Title     : assembly
Usage     : $contig->assembly($assembly);
Function  : Get/Set assembly object for this contig
Returns   : a Bio::Assembly::Scaffold object
Argument  : a Bio::Assembly::Scaffold object

strand

Title     : strand
Usage     : $contig->strand($num);
Function  : Get/Set contig orientation in a scaffold/assembly.
            Its equivalent to the strand property of sequence
            objects and sets whether the contig consensus should
            be reversed and complemented before being added to a
            scaffold or assembly.
Returns   : integer
Argument  : 1 if orientaion is forward, -1 if reverse and
            0 if none

upstream_neighbor

Title     : upstream_neighbor
Usage     : $contig->upstream_neighbor($contig);
Function  : Get/Set a contig neighbor for the current contig when
            building a scaffold. The upstream neighbor is
            located before $contig first base
Returns   : nothing
Argument  : Bio::Assembly::Contig

downstream_neighbor

Title     : downstream_neighbor
Usage     : $contig->downstream_neighbor($num);
Function  : Get/Set a contig neighbor for the current contig when
            building a scaffold. The downstream neighbor is
            located after $contig last base
Returns   : nothing
Argument  : Bio::Assembly::Contig

Contig feature collection methods

add_features

Title     : add_features
Usage     : $contig->add_features($feat,$flag)
Function  :

            Add an array of features to the contig feature
            collection. The consensus sequence may be attached to the
            added feature, if $flag is set to 1. If $flag is 0 and
            the feature attached to one of the contig aligned
            sequences, the feature is registered as an aligned
            sequence feature. If $flag is 0 and the feature is not
            attched to any sequence in the contig, the feature is
            simply added to the feature collection and no attachment
            or registration is made.

            Note: You must attach aligned sequences to their features
            prior to calling add_features, otherwise you won't be
            able to access the feature through get_seq_feat_by_tag()
            method.

Returns   : number of features added.
Argument  :
            $feat : A reference to an array of Bio::SeqFeatureI
            $flag : boolean - true if consensus sequence object
                    should be attached to this feature, false if
                    no consensus attachment should be made.
                    Default: false.

remove_features

Title     : remove_features
Usage     : $contig->remove_features(@feat)
Function  : Remove an array of contig features
Returns   : true if successful
Argument  : An array of Bio::SeqFeature::Generic (Bio::SeqFeatureI)

get_features_collection

Title     : get_features_collection
Usage     : $contig->get_features_collection()
Function  : Get the collection of all contig features and seqfeatures
Returns   : Bio::DB::SeqFeature::Store (Bio::SeqFeature::CollectionI)
Argument  : none

remove_features_collection

Title     : remove_features_collection
Usage     : $contig->remove_features_collection()
Function  : Remove the collection of all contig features. It is useful
            to save some memory (when contig features are not needed).
Returns   : none
Argument  : none

Coordinate system's related methods

See Coordinate_Systems above.

change_coord

Title     : change_coord
Usage     : $contig->change_coord($in,$out,$query)
Function  :

            Change coordinate system for $query.  This method
            transforms locations between coordinate systems described
            in section "Coordinate Systems" of this document.

            Note: this method will throw an exception when changing
            coordinates between "ungapped consensus" and other
            systems if consensus sequence was not set. It will also
            throw exceptions when changing coordinates among aligned
            sequence, either with or without gaps, and other systems
            if sequence locations were not set with set_seq_coord().

Returns   : integer
Argument  :
            $in    : [string]  input coordinate system
            $out   : [string]  output coordinate system
            $query : [integer] a position in a sequence

get_seq_coord

Title     : get_seq_coord
Usage     : $contig->get_seq_coord($seq);
Function  : Get "gapped consensus" location for aligned sequence
Returns   : Bio::SeqFeature::Generic for coordinates or undef.
            A warning is printed if sequence coordinates were not set.
Argument  : Bio::LocatableSeq object

set_seq_coord

Title     : set_seq_coord
Usage     : $contig->set_seq_coord($feat,$seq);
Function  :

            Set "gapped consensus" location for an aligned
            sequence. If the sequence was previously added using
            add_seq, its coordinates are changed/set.  Otherwise,
            add_seq is called and the sequence is added to the
            contig.

Returns   : Bio::SeqFeature::Generic for old coordinates or undef.
Argument  :
            $feat  : a Bio::SeqFeature::Generic object
                     representing a location for the
                     aligned sequence, in "gapped
                     consensus" coordinates.

            Note: the original feature primary tag will
                  be lost.

            $seq   : a Bio::LocatableSeq object

Bio::Assembly::Contig consensus methods

set_consensus_sequence

Title     : set_consensus_sequence
Usage     : $contig->set_consensus_sequence($seq)
Function  : Set the consensus sequence object for this contig
Returns   : consensus length
Argument  : Bio::LocatableSeq

set_consensus_quality

Title     : set_consensus_quality
Usage     : $contig->set_consensus_quality($qual)
Function  : Set the quality object for consensus sequence
Returns   : nothing
Argument  : Bio::Seq::QualI object

get_consensus_length

Title     : get_consensus_length
Usage     : $contig->get_consensus_length()
Function  : Get consensus sequence length
Returns   : integer
Argument  : none

get_consensus_sequence

Title     : get_consensus_sequence
Usage     : $contig->get_consensus_sequence()
Function  : Get a reference to the consensus sequence object
            for this contig
Returns   : Bio::SeqI object
Argument  : none

get_consensus_quality

Title     : get_consensus_quality
Usage     : $contig->get_consensus_quality()
Function  : Get a reference to the consensus quality object
            for this contig.
Returns   : A Bio::Seq::QualI object
Argument  : none

Bio::Assembly::Contig aligned sequences methods

set_seq_qual

Title     : set_seq_qual
Usage     : $contig->set_seq_qual($seq,$qual);
Function  : Adds quality to an aligned sequence.
Returns   : nothing
Argument  : a Bio::LocatableSeq object and
            a Bio::Seq::QualI object

See Bio::LocatableSeq for more information.

get_seq_ids

Title     : get_seq_ids
Usage     : $contig->get_seq_ids( -start => $start,
                                  -end   => $end,
                                  -type  => "gapped A0QR67B08.b" );
Function  : Get list of sequence IDs overlapping interval [$start, $end]
            The default interval is [1,$contig->length]
            Default coordinate system is "gapped contig"
Returns   : An array
Argument  : A hash with optional elements:
            -start : consensus subsequence start
            -end   : consensus subsequence end
            -type  : the coordinate system type for $start and $end arguments
                     Coordinate system available are:
                     "gapped consensus"   : consensus coordinates with gaps
                     "ungapped consensus" : consensus coordinates without gaps
                     "aligned $ReadID"    : read $ReadID coordinates with gaps
                     "unaligned $ReadID"  : read $ReadID coordinates without gaps

get_seq_feat_by_tag

Title     : get_seq_feat_by_tag
Usage     : $seq = $contig->get_seq_feat_by_tag($seq,"_aligned_coord:$seqID")
Function  : Get a sequence feature based on its primary_tag.
Returns   : a Bio::SeqFeature object
Argument  : a Bio::LocatableSeq and a string (feature primary tag)

get_seq_by_name

Title     : get_seq_by_name
Usage     : $seq = $contig->get_seq_by_name('Seq1')
Function  : Gets a sequence based on its id.
Returns   : a Bio::LocatableSeq object
            undef if name is not found
Argument  : string

get_qual_by_name

Title     : get_qual_by_name
Usage     : $seq = $contig->get_qual_by_name('Seq1')
Function  :

            Gets Bio::Seq::QualI object for a sequence
            through its id ( as given by $qual->id() ).

Returns   : a Bio::Seq::QualI object.
            undef if name is not found
Argument  : string

Bio::Align::AlignI compatible methods

Modifier methods

These methods modify the MSE by adding, removing or shuffling complete sequences.

add_seq

Title     : add_seq
Usage     : $contig->add_seq($newseq);
Function  :

            Adds a sequence to the contig. *Does*
            *not* align it - just adds it to the
            hashes.

Returns   : nothing
Argument  : a Bio::LocatableSeq object

See Bio::LocatableSeq for more information.

remove_seq

Title     : remove_seq
Usage     : $contig->remove_seq($seq);
Function  : Removes a single sequence from a contig
Returns   : 1 on success, 0 otherwise
Argument  : a Bio::LocatableSeq object

purge

Title   : purge
Usage   : $contig->purge(0.7);
Function:

          Removes sequences above whatever %id.

          This function will grind on large alignments. Beware!
          (perhaps not ideally implemented)

Example :
Returns : An array of the removed sequences
Argument:

sort_alphabetically

Title     : sort_alphabetically
Usage     : $contig->sort_alphabetically
Function  :

            Changes the order of the alignemnt to alphabetical on name
            followed by numerical by number.

Returns   :
Argument  :

Sequence selection methods

Methods returning one or more sequences objects.

each_seq

Title     : each_seq
Usage     : foreach $seq ( $contig->each_seq() )
Function  : Gets an array of Seq objects from the alignment
Returns   : an array
Argument  :

each_alphabetically

Title     : each_alphabetically
Usage     : foreach $seq ( $contig->each_alphabetically() )
Function  :

            Returns an array of sequence object sorted alphabetically
            by name and then by start point.
            Does not change the order of the alignment

Returns   :
Argument  :

each_seq_with_id

Title     : each_seq_with_id
Usage     : foreach $seq ( $contig->each_seq_with_id() )
Function  :

            Gets an array of Seq objects from the
            alignment, the contents being those sequences
            with the given name (there may be more than one)

Returns   : an array
Argument  : a seq name

get_seq_by_pos

Title     : get_seq_by_pos
Usage     : $seq = $contig->get_seq_by_pos(3)
Function  :

            Gets a sequence based on its position in the alignment.
            Numbering starts from 1.  Sequence positions larger than
            num_sequences() will thow an error.

Returns   : a Bio::LocatableSeq object
Argument  : positive integer for the sequence osition

Create new alignments

The result of these methods are horizontal or vertical subsets of the current MSE.

select

Title     : select
Usage     : $contig2 = $contig->select(1, 3) # three first sequences
Function  :

            Creates a new alignment from a continuous subset of
            sequences.  Numbering starts from 1.  Sequence positions
            larger than num_sequences() will thow an error.

Returns   : a Bio::Assembly::Contig object
Argument  : positive integer for the first sequence
            positive integer for the last sequence to include (optional)

select_noncont

Title     : select_noncont
Usage     : $contig2 = $contig->select_noncont(1, 3) # first and 3rd sequences
Function  :

            Creates a new alignment from a subset of
            sequences.  Numbering starts from 1.  Sequence positions
            larger than num_sequences() will throw an error.

Returns   : a Bio::Assembly::Contig object
Args      : array of integers for the sequences

slice

Title     : slice
Usage     : $contig2 = $contig->slice(20, 30)
Function  :

            Creates a slice from the alignment inclusive of start and
            end columns.  Sequences with no residues in the slice are
            excluded from the new alignment and a warning is printed.
            Slice beyond the length of the sequence does not do
            padding.

Returns   : a Bio::Assembly::Contig object
Argument  : positive integer for start column
            positive integer for end column

Change sequences within the MSE

These methods affect characters in all sequences without changeing the alignment.

map_chars

Title     : map_chars
Usage     : $contig->map_chars('\.','-')
Function  :

            Does a s/$arg1/$arg2/ on the sequences. Useful for gap
            characters

            Notice that the from (arg1) is interpretted as a regex,
            so be careful about quoting meta characters (eg
            $contig->map_chars('.','-') wont do what you want)

Returns   :
Argument  : 'from' rexexp
            'to' string

uppercase

Title     : uppercase()
Usage     : $contig->uppercase()
Function  : Sets all the sequences to uppercase
Returns   :
Argument  :

match_line

Title    : match_line()
Usage    : $contig->match_line()
Function : Generates a match line - much like consensus string
           except that a line indicating the '*' for a match.
Argument : (optional) Match line characters ('*' by default)
           (optional) Strong match char (':' by default)
           (optional) Weak match char ('.' by default)

match

Title     : match()
Usage     : $contig->match()
Function  :

            Goes through all columns and changes residues that are
            identical to residue in first sequence to match '.'
            character. Sets match_char.

            USE WITH CARE: Most MSE formats do not support match
            characters in sequences, so this is mostly for output
            only. NEXUS format (Bio::AlignIO::nexus) can handle
            it.

Returns   : 1
Argument  : a match character, optional, defaults to '.'

unmatch

Title     : unmatch()
Usage     : $contig->unmatch()
Function  :

            Undoes the effect of method match. Unsets match_char.

Returns   : 1
Argument  : a match character, optional, defaults to '.'

MSE attibutes

Methods for setting and reading the MSE attributes.

Note that the methods defining character semantics depend on the user to set them sensibly. They are needed only by certain input/output methods. Unset them by setting to an empty string ('').

id

Title     : id
Usage     : $contig->id("Ig")
Function  : Gets/sets the id field of the alignment
Returns   : An id string
Argument  : An id string (optional)

missing_char

Title     : missing_char
Usage     : $contig->missing_char("?")
Function  : Gets/sets the missing_char attribute of the alignment
            It is generally recommended to set it to 'n' or 'N'
            for nucleotides and to 'X' for protein.
Returns   : An missing_char string,
Argument  : An missing_char string (optional)

match_char

Title     : match_char
Usage     : $contig->match_char('.')
Function  : Gets/sets the match_char attribute of the alignment
Returns   : An match_char string,
Argument  : An match_char string (optional)

gap_char

Title     : gap_char
Usage     : $contig->gap_char('-')
Function  : Gets/sets the gap_char attribute of the alignment
Returns   : An gap_char string, defaults to '-'
Argument  : An gap_char string (optional)

symbol_chars

Title   : symbol_chars
Usage   : my @symbolchars = $contig->symbol_chars;
Function: Returns all the seen symbols (other than gaps)
Returns : array of characters that are the seen symbols
Argument: boolean to include the gap/missing/match characters

Alignment descriptors

These read only methods describe the MSE in various ways.

consensus_string

Title     : consensus_string
Usage     : $str = $contig->consensus_string($threshold_percent)
Function  : Makes a strict consensus
Returns   :
Argument  : Optional threshold ranging from 0 to 100.
            The consensus residue has to appear at least threshold %
            of the sequences at a given location, otherwise a '?'
            character will be placed at that location.
            (Default value = 0%)

consensus_iupac

Title     : consensus_iupac
Usage     : $str = $contig->consensus_iupac()
Function  :

            Makes a consensus using IUPAC ambiguity codes from DNA
            and RNA. The output is in upper case except when gaps in
            a column force output to be in lower case.

            Note that if your alignment sequences contain a lot of
            IUPAC ambiquity codes you often have to manually set
            alphabet.  Bio::PrimarySeq::_guess_type thinks they
            indicate a protein sequence.

Returns   : consensus string
Argument  : none
Throws    : on protein sequences

is_flush

Title     : is_flush
Usage     : if( $contig->is_flush() )
          :
          :
Function  : Tells you whether the alignment
          : is flush, ie all of the same length
          :
          :
Returns   : 1 or 0
Argument  :

length

Title     : length()
Usage     : $len = $contig->length()
Function  : Returns the maximum length of the alignment.
            To be sure the alignment is a block, use is_flush
Returns   :
Argument  :

maxname_length

Title     : maxname_length
Usage     : $contig->maxname_length()
Function  :

            Gets the maximum length of the displayname in the
            alignment. Used in writing out various MSE formats.

Returns   : integer
Argument  :

num_residues

Title     : num_residues
Usage     : $no = $contig->num_residues
Function  : number of residues in total in the alignment
Returns   : integer
Argument  :
Note      : replaces no_residues

num_sequences

Title     : num_sequences
Usage     : $depth = $contig->num_sequences
Function  : number of sequence in the sequence alignment
Returns   : integer
Argument  : None
Note      : replaces no_sequences

percentage_identity

Title   : percentage_identity
Usage   : $id = $contig->percentage_identity
Function: The function calculates the percentage identity of the alignment
Returns : The percentage identity of the alignment (as defined by the
                            implementation)
Argument: None

overall_percentage_identity

Title   : percentage_identity
Usage   : $id = $contig->percentage_identity
Function: The function calculates the percentage identity of
          the conserved columns
Returns : The percentage identity of the conserved columns
Args    : None

average_percentage_identity

Title   : average_percentage_identity
Usage   : $id = $contig->average_percentage_identity
Function: The function uses a fast method to calculate the average
          percentage identity of the alignment
Returns : The average percentage identity of the alignment
Args    : None

Alignment positions

Methods to map a sequence position into an alignment column and back. column_from_residue_number() does the former. The latter is really a property of the sequence object and can done using Bio::LocatableSeq::location_from_column:

# select somehow a sequence from the alignment, e.g.
my $seq = $contig->get_seq_by_pos(1);
#$loc is undef or Bio::LocationI object
my $loc = $seq->location_from_column(5);

column_from_residue_number

Title   : column_from_residue_number
Usage   : $col = $contig->column_from_residue_number( $seqname, $resnumber)
Function:

          This function gives the position in the alignment
          (i.e. column number) of the given residue number in the
          sequence with the given name. For example, for the
          alignment

          Seq1/91-97 AC..DEF.GH
          Seq2/24-30 ACGG.RTY..
          Seq3/43-51 AC.DDEFGHI

          column_from_residue_number( "Seq1", 94 ) returns 5.
          column_from_residue_number( "Seq2", 25 ) returns 2.
          column_from_residue_number( "Seq3", 50 ) returns 9.

          An exception is thrown if the residue number would lie
          outside the length of the aligment
          (e.g. column_from_residue_number( "Seq2", 22 )

     Note: If the the parent sequence is represented by more than
     one alignment sequence and the residue number is present in
     them, this method finds only the first one.

Returns : A column number for the position in the alignment of the
          given residue in the given sequence (1 = first column)
Args    : A sequence id/name (not a name/start-end)
          A residue number in the whole sequence (not just that
          segment of it in the alignment)

Sequence names

Methods to manipulate the display name. The default name based on the sequence id and subsequence positions can be overridden in various ways.

displayname

Title     : displayname
Usage     : $contig->displayname("Ig", "IgA")
Function  : Gets/sets the display name of a sequence in the alignment
          :
Returns   : A display name string
Argument  : name of the sequence
            displayname of the sequence (optional)

set_displayname_count

Title     : set_displayname_count
Usage     : $contig->set_displayname_count
Function  :

            Sets the names to be name_# where # is the number of
            times this name has been used.

Returns   : None
Argument  : None

set_displayname_flat

Title     : set_displayname_flat
Usage     : $contig->set_displayname_flat()
Function  : Makes all the sequences be displayed as just their name,
            not name/start-end
Returns   : 1
Argument  : None

set_displayname_normal

Title     : set_displayname_normal
Usage     : $contig->set_displayname_normal()
Function  : Makes all the sequences be displayed as name/start-end
Returns   : None
Argument  : None

Internal Methods

Title     : _binary_search
Usage     : _binary_search($list,$query)
Function  :

            Find a number in a sorted list of numbers.  Return values
            may be on or two integers. One positive integer or zero
            (>=0) is the index of the element that stores the queried
            value.  Two positive integers (or zero and another
            number) are the indexes of elements among which the
            queried value should be placed. Negative single values
            mean:

            -1: $query is smaller than smallest element in list
            -2: $query is greater than greatest element in list

Returns   : array of integers
Argument  :
            $list  : array reference
            $query : integer

_compare

Title   : _compare
Usage   : _compare($arg1,$arg2)
Function: Perform numeric or string comparisons
Returns : integer (0, 1 or -1)
Args    : values to be compared

_nof_gaps

Title   : _nof_gaps
Usage   : _nof_gaps($array_ref, $query)
Function: number of gaps found before position $query
Returns : integer
Args    :
          $array_ref : gap registry reference
          $query     : [integer] a position in a sequence

_padded_unpadded

Title   : _padded_unpadded
Usage   : _padded_unpadded($array_ref, $query)
Function:

          Returns a coordinate corresponding to
          position $query after gaps were
          removed from a sequence.

Returns : integer
Args    :
          $array_ref : reference to this gap registry
          $query     : [integer] coordionate to change

_unpadded_padded

Title   : _unpadded_padded
Usage   : _unpadded_padded($array_ref, $query)
Function:

          Returns the value corresponding to
          ungapped position $query when gaps are
          counted as valid sites in a sequence

Returns :
Args    : $array_ref = a reference to this sequence's gap registry
          $query = [integer] location to change

_register_gaps

Title   : _register_gaps
Usage   : $self->_register_gaps($seq, $array_ref)
Function: stores gap locations for a sequence
Returns : number of gaps found
Args    :
          $seq       : sequence string
          $array_ref : a reference to an array,
                       where gap locations will
                       be stored

Deprecated methods

no_residues

Title     : no_residues
Usage     : $no = $ali->no_residues
Function  : number of residues in total in the alignment
Returns   : integer
Argument  :
Note      : deprecated in favor of num_residues() 

no_sequences

Title     : no_sequences
Usage     : $depth = $ali->no_sequences
Function  : number of sequence in the sequence alignment
Returns   : integer
Argument  :
Note      : deprecated in favor of num_sequences()