[Bioperl-l] Fitch methode

[Jason Stajich]

It assumes that you have assigned trait values to all nodes in the tree, the key is assigned when you do an add_trait on a tree. 

You can see how to add traits and some sample data if you look in the t/Tree/Statistics.t code and you'll see the assignment of the $key 
 my $key = $tree->add_trait(test_input_file('traits.tab'));

>From the documentation:

   Tree‐Trait statistics
       The following methods produce descriptors of trait distribution among
       leaf nodes within the trees. They require that a trait has been set for
       each leaf node. The tag methods of Bio::Tree::Node are used to store
       them as key/value pairs. In this way, one tree can store more than one
       trait.

       Trees have method add_traits() to set trait values from a file. See the
       add_trait() method in Bio::Tree::TreeFunctionsI.

   fitch
         Example    : fitch($tree, $key, $node);
         Description: Calculates Parsimony Score (PS) and internal trait
                      values using the Fitch 1971 parsimony algorithm for
                      the subtree a defined by the (internal) node.
                      Node defaults to the root.
         Returns    : true on success
         Exceptions : leaf nodes have to have the trait defined
         Args       : 1. Bio::Tree::TreeI object
                      2. trait name string
                      3. Bio::Tree::NodeI object within the tree, optional

       Runs first fitch_up that calculates parsimony scores and then
       fitch_down that should resolve most of the trait/character state
       ambiguities.

       Fitch, W.M., 1971. Toward defining the course of evolution: minimal
       change for a specific tree topology. Syst. Zool. 20, 406−416.

       You can access calculated parsimony values using:

         $score = $node−>−>get_tag_values('ps_score');

       and the trait value with:

         $traitvalue = $node−>−>get_tag_values('ps_trait'); # only the first
         @traitvalues = $node−>−>get_tag_values('ps_trait');

       Note that there can be more that one trait value, especially for the
       root node.

Documentation rendered in Pdoc:
http://docs.bioperl.org/bioperl-live/Bio/Tree/Statistics.html#POD3

Here is the documentation for add_traits from the 
  add_trait
        Title   : add_trait
        Usage   : my $key = $tree−>add_trait($trait_file, 3);
        Function: Add traits to the leaf nodes of a Bio::Tree:Tree from a file.
                  The trait file is a tab−delimited text file and needs to have a
                  header line giving names to traits. The first column contains the
                  leaf node ids. Subsequent columns contain different trait value sets.
                  Single or double quotes are removed from the trait values. Traits
                  are added to leaf nodes as a tag named $key using the add_tag_value()
                  method. This means that you can retrieve the trait values using the
                  get_tag_values() method (see the documentation for Bio::Tree::Node).
        Returns : Trait name (a scalar) on success, undef on failure (for example, if
                  the column index requested was too large).
        Args    : * Name of trait file (scalar string).
                  * Index of trait file column (scalar int). Note that numbering starts
                    at 0. Default: 1 (second column).
                  * Ignore missing values. Typically, if a leaf node has no value in
                    the trait file, an exception is thrown. If you set this option to
                    1, then no trait will be given to the node (no exception thrown).

also see the documentation rendered in Pdoc:
http://docs.bioperl.org/bioperl-live/Bio/Tree/TreeFunctionsI.html#POD19
On Oct 9, 2012, at 1:15 PM, Alexandre Miranda <amiranda65 at gmail.com> wrote:

> Hello,
> 
> I desperately try to implement the methode Fitch from the library
> Bio:Tree:Statistics.
> 
> But I cannot understand what kind of parameter I should used for the $key
> value : fitch($tree, $key, $node);
> 
> Can you please send me a sample of code using that methode ?
> 
> thanks for your quick reply.
> 
> Best Regards,
> 
> Alexandre
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> Bioperl-l mailing list
> Bioperl-l at lists.open-bio.org
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Jason Stajich
jason.stajich at gmail.com
jason at bioperl.org