# NAME

Algorithm::DistanceMatrix - Compute distance matrix for any distance metric

# VERSION

version 0.04

# SYNOPSIS

```
use Algorithm::DistanceMatrix;
my $m = Algorithm::DistanceMatrix->new(
metric=>\&mydistance,objects=\@myarray);
my $distmatrix = $m->distancematrix;
use Algorithm::Cluster qw/treecluster/;
# method=>
# s: single-linkage clustering
# http://en.wikipedia.org/wiki/Single-linkage_clustering
# m: maximum- (or complete-) linkage clustering
# http://en.wikipedia.org/wiki/Complete_linkage_clustering
# a: average-linkage clustering (UPGMA)
# http://en.wikipedia.org/wiki/UPGMA
my $tree = treecluster(data=>$distmat, method=>'a');
# Get your objects and the cluster IDs they belong to, assuming 5 clusters
my $cluster_ids = $tree->cut(5);
# Index corresponds to that of the original objects
print $objects->[2], ' belongs to cluster ', $cluster_ids->[2], "\n";
```

# DESCRIPTION

This is a small helper package for Algorithm::Cluster. That module provides many facilities for clustering data. It also provides a `distancematrix`

function, but assumes tabular data, which is the standard for gene expression data.

If your data is tabular, you should first have a look at `distancematrix`

in Algorithm::Cluster

` http://cpansearch.perl.org/src/MDEHOON/Algorithm-Cluster-1.48/doc/cluster.pdf`

Otherwise, this package provides a simple distance matrix, given an arbitrary distance function. It does not assume anything about your data. You simply provide a callback function for measuring the distance between any two objects. It produces a lower diagonal (by default) distance matrix that is fit to be used by the clustering algorithms of Algorithm::Cluster.

# NAME

Algorithm::DistanceMatrix - Compute distance matrix for any distance metric

# VERSION

version 0.04

# METHODS

## mode

One of `qw/lower upper full/`

for a lower diagonal, upper diagonal, or full distance matrix.

## metric

Callback for computing the distance, similarity, or whatever measure you like.

` $matrix->metric(\@mydistance);`

Where `mydistance`

receives two objects as it's first two arguments.

If you need to pass special parameters to your method:

` $matrix->metric(sub{my($x,$y)=@_;mydistance(first=>$x,second=>$y,mode=>'fast')};`

You may use any metric, and may return any number or object. Note that if you plan to use this with Algorithm::Cluster this needs to be a distance metric. So, if you're measure how similar two things are, on a scale of 1-10, then you should return `10-$similarity`

to get a distance.

Default is the absolute values of the scalar difference (i.e. `abs(X-Y)`

)

## objects

Array reference. Doesn't matter what kind of objects are in the array, as long as your `metric`

can process them.

## distancematrix

2D array of distances (or similarities, or whatever) between your objects.

(An ArrayRef of ArrayRefs.)

# AUTHOR

Chad A. Davis <chad.a.davis@gmail.com>

# COPYRIGHT AND LICENSE

This software is copyright (c) 2011 by Chad A. Davis.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.