Bio::Community::Tools::Rarefier - Normalize communities by count
use Bio::Community::Tools::Rarefier; # Normalize communities in a metacommunity by repeatedly taking 1,000 random members my $rarefier = Bio::Community::Tools::Rarefier->new( -metacommunity => $meta, -sample_size => 1000, -threshold => 0.001, # stop bootstrap iterations when threshold is reached ); # Rarefied results, with decimal counts my $average_community = $rarefier->get_avg_meta->; # Round counts to integer numbers my $representative_community = $rarefier->get_repr_meta->; # Alternatively, specify a number of repetitions my $rarefier = Bio::Community::Tools::Rarefier->new( -metacommunity => $meta, -sample_size => 1000, -num_repetitions => 0.001, # stop after this number of bootstrap iterations ); # ... or assume an infinite number of repetitions my $rarefier = Bio::Community::Tools::Rarefier->new( -metacommunity => $meta, -sample_size => 1000, -num_repetitions => 'inf', );
This module takes a metacommunity and normalizes (rarefies) the communities it contains by their number of counts.
Comparing the composition and diversity of biological communities can be biased by sampling artefacts. When comparing two identical communities, one for which 10,000 counts were made to one, to one with only 1,000 counts, the smaller community will appear less diverse. A solution is to repeatedly bootstrap the larger communities by taking 1,000 random members from it.
This module uses Bio::Community::Sampler to take random member from communities and normalize them by their number of counts. After all random repetitions have been performed, average communities or representative communities are returned. These communities all have the same number of counts.
Florent Angly firstname.lastname@example.org
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Copyright 2011-2014 by Florent Angly <firstname.lastname@example.org>
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.1 or, at your option, any later version of Perl 5 you may have available.
The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _
Function: Create a new Bio::Community::Tool::Rarefier object Usage : my $rarefier = Bio::Community::Tool::Rarefier->new( ); Args : -metacommunity : see metacommunity() -num_repetitions: see num_repetitions() -sample_size : see sample_size() -seed : see set_seed() Returns : a new Bio::Community::Tools::Rarefier object
Function: Get or set the metacommunity to normalize. Usage : my $meta = $rarefier->metacommunity; Args : A Bio::Community::Meta object Returns : A Bio::Community::Meta object
Function: Get or set the sample size, i.e. the number of members to pick randomly at each iteration. It has to be smaller than the total count of the smallest community or an error will be generated. If the sample size is omitted, it defaults to the get_members_count() of the smallest community. Usage : my $sample_size = $rarefier->sample_size; Args : integer for the sample size Returns : integer for the sample size
Function: Get or set the threshold. While iterating, when the beta diversity or distance between the average community and the average community at the previous iteration decreases below this threshold, the bootstrapping is stopped. By default, the threshold is 1e-5. The num_repetitions() method provides an alternative way to specify when to stop the computation. After communities have been normalized using the num_repetitions() method instead of the threshold() method, the beta diversity between the last two average communities repetitions can be accessed using the threshold() method. Usage : my $threshold = $rarefier->threshold; Args : positive integer for the number of repetitions Returns : positive integer for the (minimum) number of repetitions
Function: Get or set the number of bootstrap repetitions to perform. When given, instead of relying on the threshold() to determine when to stop repeating the bootstrap process, perform an arbitrary number of repetitions. After communities have been normalized by count using threshold() method, the number of repetitions actually done can be accessed using this method. As a special case, specify 'inf' to simulate an infinite number of repetitions. Usage : my $repetitions = $rarefier->repetitions; Args : positive integer or 'inf' number of repetitions Returns : positive integer for the (minimum) number of repetitions
Usage : $sampler->set_seed(1234513451); Function: Get or set the seed used to pick the random members. Args : Positive integer Returns : Positive integer
Function: Get or set verbose mode. In verbose mode, the current number of iterations (and beta diversity if a threshold is used) is displayed. Usage : $rarefier->verbose(1); Args : 0 (default) or 1 Returns : 0 or 1
Function: Get or set drop mode. In drop mode, this module silently drops communities that do not have enough members instead of reporting an error. Usage : $rarefier->drop(1); Args : 0 (default) or 1 Returns : 0 or 1
Function: Calculate an average metacommunity. Usage : my $meta = $rarefier->get_avg_meta; Args : none Returns : Bio::Community::Meta object
Function: Calculate a representative metacommunity. Usage : my $meta = $rarefier->get_repr_meta; Args : none Returns : Bio::Community::Meta object