Bio::Assembly::Tools::ContigSpectrum(3)

NAME
Bio::Assembly::Tools::ContigSpectrum - create and manipulate contig spectra

SYNOPSIS
  # Simple contig spectrum creation
  my $csp1 = Bio::Assembly::Tools::ContigSpectrum->new(
    -id       => 'csp1',
    -spectrum => { 1 => 10,
                   2 => 2,
                   3 => 1 } );

  # ...or another way to create a simple contig spectrum
  my $csp2 = Bio::Assembly::Tools::ContigSpectrum->new;
  $csp2->id('csp2');
  $csp2->spectrum({ 1 => 20, 2 => 1, 4 => 1 });

  # Get some information
  print "This is contig spectrum ".$csp->id."\n";
  print "It contains ".$csp->nof_seq." sequences\n";
  print "The largest contig has ".$csp->max_size." sequences\n";
  print "The spectrum is: ".$csp->to_string($csp->spectrum)."\n";

  # Let's add the contig spectra
  my $summed_csp = Bio::Assembly::Tools::ContigSpectrum->new;
  $summed_csp->add($csp1);
  $summed_csp->add($csp2);
  print "The summed contig spectrum is ".$summed_csp->to_string."\n";

  # Make an average
  my $avg_csp = Bio::Assembly::Tools::ContigSpectrum->new;
  $avg_csp = $avg_csp->average([$csp1, $csp2]);
  print "The average contig spectrum is ".$avg_csp->to_string."\n";

  # Get a contig spectrum from an assembly
  my $from_assembly = Bio::Assembly::Tools::ContigSpectrum->new(
    -assembly       => $assembly_object,
    -eff_asm_params => 1);
  print "The contig spectrum from assembly is ".$from_assembly->to_string."\n";

  # Report advanced information (possible because eff_asm_params = 1)
  print "Average sequence length: ".$from_assembly->avg_seq_length." bp\n";
  print "Minimum overlap length: ".$from_assembly->min_overlap." bp\n";
  print "Average overlap length: ".$from_assembly->avg_overlap." bp\n";
  print "Minimum overlap match: ".$from_assembly->min_identity." %\n";
  print "Average overlap match: ".$from_assembly->avg_identity." %\n";

  # Assuming the assembly object contains sequences from several different
  # metagenomes, we have a mixed contig spectrum from which a cross contig
  # spectrum and dissolved contig spectra can be obtained
  my $mixed_csp = $from_assembly;

  # Calculate a dissolved contig spectrum
  my $meta1_dissolved = Bio::Assembly::Tools::ContigSpectrum->new(
    -dissolve => [$mixed_csp, 'metagenome1'] );
  my $meta2_dissolved = Bio::Assembly::Tools::ContigSpectrum->new(
    -dissolve => [$mixed_csp, 'metagenome2'] );
  print "The dissolved contig spectra are:\n".
    $meta1_dissolved->to_string."\n".
    $meta2_dissolved->to_string."\n";

  # Determine a cross contig spectrum
  my $cross_csp = Bio::Assembly::Tools::ContigSpectrum->new(
    -cross => $mixed_csp );
  print "The cross contig spectrum is ".$cross_csp->to_string."\n";

  # Score a contig spectrum (the more abundant the contigs and the larger their
  # size, the larger the score)

DESCRIPTION
The Bio::Assembly::Tools::ContigSpectrum Perl module enables to manually create contig spectra, import them from assemblies, manipulate them, transform between different types of contig spectra and output them.

Bio::Assembly::Tools::ContigSpectrum is a module to create, manipulate and output contig spectra, assembly-derived data used in metagenomics (community genomics) for diversity estimation.

  Background
A contig spectrum is the count of the number of contigs of different size in an assembly. For example, the contig spectrum [100 5 1 0 0 ...] means that there were 100 singlets (1-contigs), 5 contigs of 2 sequences (2-contigs), 1 contig of 3 sequences (3-contig) and no larger contigs.

An assembly can be produced from a mixture of sequences from different metagenomes. The contig obtained from this assembly is a mixed contig spectrum. The contribution of each metagenome in this mixed contig spectrum can be obtained by determining a dissolved contig spectrum.

Finally, based on a mixed contig spectrum, a cross contig spectrum can be determined. In a cross contig spectrum, only contigs containing sequences from different metagenomes are kept; "pure" contigs are excluded. Additionally, the total number of singletons (1-contigs) from each region that assembles with any fragments from other regions is the number of 1-contigs in the cross contig spectrum.

  Implementation
The simplest representation of a contig spectrum is as a hash representation where the key is the contig size (number of sequences making up the contig) and the value the number of contigs of this size.

In fact, it is useful to have more information associated with the contig spectrum, hence the Bio::Assembly::Tools::ContigSpectrum module implements an object containing a contig spectrum hash and additional information. The get/set methods to access them are:

    id              contig spectrum ID
    nof_seq         number of sequences
    nof_rep         number of repetitions (assemblies) used
    max_size        size of (number of sequences in) the largest contig
    nof_overlaps    number of overlaps
    min_overlap     minimum overlap length for building a contig
    min_identity    minimum sequence identity over the overlap length
    avg_overlap     average overlap length
    avg_identity    average overlap identity
    avg_seq_length  average sequence length
    eff_asm_params  effective assembly parameters
    spectrum        hash representation of a contig spectrum

  Operations on the contig spectra:

    to_string       create a string representation of the spectrum
    spectrum        import a hash contig spectrum
    assembly        determine a contig spectrum from an assembly
    dissolve        calculate a dissolved contig spectrum (based on assembly)
    cross           produce a cross contig spectrum (based on assembly)
    add             add a contig spectrum to an existing one
    average         make an average of several contig spectra

When using operations that rely on knowing "where" (from what metagenomes) a sequence came from (i.e. when creating a dissolved or cross contig spectrum), make sure that the sequences used for the assembly have a name header, e.g. >metagenome1|seq1, >metagenome2|seq1, ...

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 email or the web:

  bioperl-bugs@bio.perl.org
  http://bugzilla.bioperl.org/

AUTHOR - Florent E Angly
Email florent_dot_angly_at_gmail_dot_com

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

  new
  Title   : new
  Usage   : my $csp = Bio::Assembly::Tools::ContigSpectrum->new();
              or
            my $csp = Bio::Assembly::Tools::ContigSpectrum->new(
              -id => 'some_name',
              -spectrum =>  { 1 => 90 , 2 => 3 , 4 => 1 },
            );
              or
            my $csp = Bio::Assembly::Tools::ContigSpectrum->new(
              -assembly =>  $assembly_obj
            );
  Function: create a new contig spectrum object
  Returns : reference to a contig spectrum object
  Args    : none

  id
  Title   : id
  Usage   : $csp->id
  Function: get/set contig spectrum id
  Returns : string
  Args    : string [optional]

  nof_seq
  Title   : nof_seq
  Usage   : $csp->nof_seq
  Function: get/set the number of sequences making up the contig spectrum
  Returns : integer
  Args    : integer [optional]

  nof_rep
  Title   : nof_rep
  Usage   : $csp->nof_rep
  Function: Get/Set the number of repetitions (assemblies) used to create the
            contig spectrum
  Returns : integer
  Args    : integer [optional]

  max_size
  Title   : max_size
  Usage   : $csp->max_size
  Function: get/set the size of (number of sequences in) the largest contig
  Returns : integer
  Args    : integer [optional]

  nof_overlaps
  Title   : nof_overlaps
  Usage   : $csp->nof_overlaps
  Function: Get/Set the number of overlaps in the assembly.
  Returns : integer
  Args    : integer [optional]

  min_overlap
  Title   : min_overlap
  Usage   : $csp->min_overlap
  Function: get/set the assembly minimum overlap length
  Returns : integer
  Args    : integer [optional]

  avg_overlap
  Title   : avg_overlap
  Usage   : $csp->avg_overlap
  Function: get/set the assembly average overlap length
  Returns : decimal
  Args    : decimal [optional]

  min_identity
  Title   : min_identity
  Usage   : $csp->min_identity
  Function: get/set the assembly minimum overlap identity percent
  Returns : 0 < decimal < 100
  Args    : 0 < decimal < 100 [optional]

  avg_identity
  Title   : avg_identity
  Usage   : $csp->avg_identity
  Function: get/set the assembly average overlap identity percent
  Returns : 0 < decimal < 100
  Args    : 0 < decimal < 100 [optional]

  avg_seq_len
  Title   : avg_seq_len
  Usage   : $csp->avg_seq_len
  Function: get/set the assembly average sequence length
  Returns : avg_seq_len
  Args    : real [optional]

  eff_asm_params
  Title   : eff_asm_params
  Usage   : $csp->eff_asm_params(1)
  Function: Get/set the effective assembly parameters option. It defines if the
            effective assembly parameters should be determined when a contig
            spectrum based or derived from an assembly is calulated. The
            effective assembly parameters include avg_seq_length, nof_overlaps,
            min_overlap, avg_overlap, min_identity and avg_identity.
            1 = get them, 0 = don't.
  Returns : integer
  Args    : integer [optional]

  spectrum
  Title   : spectrum
  Usage   : my $spectrum = $csp->spectrum({1=>10, 2=>2, 3=>1});
  Function: Get the current contig spectrum represented as a hash / Update a
            contig spectrum object based on a contig spectrum represented as a
            hash
            The hash representation of a contig spectrum is as following:
              key   -> contig size (in number of sequences)
              value -> number of contigs of this size
  Returns : contig spectrum as a hash reference
  Args    : contig spectrum as a hash reference [optional]

  assembly
  Title   : assembly
  Usage   : my @asm_list = $csp->assembly();
  Function: Get a reference to the list of assembly object reference used to
            make the contig spectrum object / Update the contig spectrum object
            based on an assembly object.
  Returns : array of Bio::Assembly::Scaffold
  Args    : Bio::Assembly::Scaffold

  drop_assembly
  Title   : drop_assembly
  Usage   : $csp->drop_assembly();
  Function: Remove all assembly objects associated with a contig spectrum.
            Assembly objects can be big. This method allows to free some memory
            when assembly information is not needed anymore.
  Returns : 1 for success, 0 for failure
  Args    : none

  dissolve
  Title   : dissolve
  Usage   : $dissolved_csp->dissolve($mixed_csp, $seq_header);
  Function: Dissolve a mixed contig spectrum for the set of sequences that
            contain the specified header, i.e. determine the contribution of
            these sequences to the mixed contig spectrum based on the assembly.
            The mixed contig spectrum object must have been created based on one
            (or several) assembly object(s). Additionally, min_overlap and
            min_identity must have been set (either manually using min_overlap
            or automatically by switching on the eff_asm_params option).
  Returns : 1 for success, 0 for failure
  Args    : Bio::Assembly::Tools::ContigSpectrum reference
            sequence header string

  cross
  Title   : cross
  Usage   : $cross_csp->cross($mixed_csp);
  Function: Calculate a cross contig_spectrum based on a mixed contig_spectrum.
  Returns : 1 for success, 0 for failure
  Args    : Bio::Assembly::Tools::ContigSpectrum reference

  to_string
  Title   : to_string
  Usage   : my $csp_string = $csp->to_string;
  Function: Convert the contig spectrum into a string (easy to print!!).
  Returns : string
  Args    : element separator (integer) [optional]
              1 -> space-separated
              2 -> tab-separated
              3 -> newline-separated

  add
  Title   : add
  Usage   : $csp->add($additional_csp);
  Function: Add a contig spectrum to an existing one: sums the spectra, update
            the number of sequences, number of repetitions, ...
  Returns : 1 for success, 0 for failure
  Args    : Bio::Assembly::Tools::ContigSpectrum object

  average
  Title   : average
  Usage   : my $avg_csp = $csp->average([$csp1, $csp2, $csp3]);
  Function: Average one contig spectrum or the sum of several contig spectra by
            the number of repetitions
  Returns : Bio::Assembly::Tools::ContigSpectrum
  Args    : Bio::Assembly::Tools::ContigSpectrum array reference
            eff_asm_params

  score
  Title   : score
  Usage   : my $score = $csp->score();
  Function: Score a contig spectrum (or cross-contig spectrum) such that the
             higher the number of contigs (or cross-contigs) and the larger their
             size, the higher the score.
             Let n   : total number of sequences
                 c_q : number of contigs of size q
                 q   : number of sequence in a contig
             We define: score = n/(n-1) * (X - 1/n)
                  where X = sum ( c_q * q^2 ) / n**2
             The score ranges from 0 (singlets only) to 1 (a single large contig)
             It is possible to specify a value for the number of sequences to
              assume in the contig spectrum.
  Returns : contig score
  Args    : number of total sequences to assume [optional]

  _naive_assembler
  Title   : _naive_assembler
  Usage   :
  Function: Determines the contig spectrum (hash representation) of a subset of
            sequences from a mixed contig spectrum by "reassembling" the
            specified sequences only based on their position in the contig. This
            naive assembly only verifies that the minimum overlap length and
            percentage identity are respected. There is no actual alignment done
  Returns : contig spectrum hash reference
  Args    : Bio::Assembly::Contig
            sequence ID array reference
            minimum overlap length (integer) [optional]
            minimum percentage identity (integer) [optional]

  _new_from_assembly
  Title   : _new_from_assembly
  Usage   :
  Function: Creates a new contig spectrum object based solely on the result of
            an assembly
  Returns : Bio::Assembly::Tools::ContigSpectrum
  Args    : Bio::Assembly::Scaffold

  _new_dissolved_csp
  Title   :
  Usage   : create a dissolved contig spectrum object
  Function:
  Returns :
  Args    :

  _new_cross_csp
  Title   :
  Usage   :
  Function: create a cross contig spectrum object
  Returns :
  Args    :

  _import_assembly
  Title   : _import_assembly
  Usage   : $csp->_import_assembly($assemblyobj);
  Function: Update a contig spectrum object based on an assembly object
  Returns : 1 for success, 0 for error
  Args    : Bio::Assembly::Scaffold assembly object

  _import_spectrum
  Title   : _import_spectrum
  Usage   : $csp->_import_spectrum({ 1 => 90 , 2 => 3 , 4 => 1 })
  Function: update a contig spectrum object based on a contig spectrum
            represented as a hash (key: contig size, value: number of contigs of
            this size)
  Returns : 1 for success, 0 for error
  Args    : contig spectrum as a hash reference

  _import_dissolved_csp
  Title   : _import_dissolved_csp
  Usage   : $csp->_import_dissolved_csp($mixed_csp, $seq_header);
  Function: Update a contig spectrum object by dissolving a mixed contig
            spectrum based on the header of the sequences
  Returns : 1 for success, 0 for error
  Args    : Bio::Assembly::Tools::ContigSpectrum
            sequence header string

  _import_cross_csp
  Title   : _import_cross_csp
  Usage   : $csp->_import_cross_csp($mixed_csp);
  Function: Update a contig spectrum object by calculating the cross contig
            spectrum based on a mixed contig spectrum
  Returns : 1 for success, 0 for error
  Args    : Bio::Assembly::Tools::ContigSpectrum

  _get_seq_stats
  Title   : _get_seq_stats
  Usage   : my $seqlength = $csp->_get_seq_stats($assemblyobj);
  Function: Get sequence statistics from an assembly:
              number of sequences, average sequence length
  Returns : number of sequences (integer)
            average sequence length (decimal)
  Args    : assembly object reference
            hash reference with the IDs of the sequences to consider [optional]

  _get_overlap_stats
  Title   : _get_overlap_stats
  Usage   : my ($minlength, $min_identity, $avglength, $avgidentity)
              = $csp->_get_overlap_stats($assemblyobj);
  Function: Get statistics about pairwise overlaps in contigs of an assembly
  Returns : number of overlaps
            minimum overlap length
            average overlap length
            minimum identity percent
            average identity percent
  Args    : assembly object reference
            hash reference with the IDs of the sequences to consider [optional]

  _overlap_alignment
  Title   : _overlap_alignment
  Usage   :
  Function: Produce an alignment of the overlapping section of two sequences of
            a contig. Minimum overlap length and percentage identity can be
            specified. Return undef if the sequences do not overlap or do not
            meet the minimum overlap criteria.
  Return  : Bio::SimpleAlign object reference
            alignment overlap length
            alignment overlap identity
  Args    : Bio::Assembly::Contig object reference
            Bio::LocatableSeq contig sequence 1
            Bio::LocatableSeq contig sequence 2
            minium overlap length [optional]
            minimum overlap percentage identity [optional]