AI::Categorizer::Experiment - Coordinate experimental results

 use AI::Categorizer::Experiment;
 my $e = new AI::Categorizer::Experiment(categories => \%categories);
 my $l = AI::Categorizer::Learner->restore_state(...path...);

 while (my $d = ... get document ...) {
   my $h = $l->categorize($d); # A Hypothesis
   $e->add_hypothesis($h, [map $_->name, $d->categories]);
 }

 print "Micro F1: ", $e->micro_F1, "\n"; # Access a single statistic
 print $e->stats_table; # Show several stats in table form

The AI::Categorizer::Experiment class helps you organize the results of categorization experiments. As you get lots of categorization results (Hypotheses) back from the Learner, you can feed these results to the Experiment class, along with the correct answers. When all results have been collected, you can get a report on accuracy, precision, recall, F1, and so on, with both macro-averaging and micro-averaging over categories.

The general execution flow when using this class is to create an Experiment object, add a bunch of Hypotheses to it, and then report on the results.

Internally, AI::Categorizer::Experiment inherits from the Statistics::Contingency. Please see the documentation of Statistics::Contingency for a description of its interface. All of its methods are available here, with the following additions:

new( categories => \%categories )

new( categories => \@categories, verbose => 1, sig_figs => 2 )

Returns a new Experiment object. A required categories parameter specifies the names of all categories in the data set. The category names may be specified either the keys in a reference to a hash, or as the entries in a reference to an array.

The new() method accepts a verbose parameter which will cause some status/debugging information to be printed to STDOUT when verbose is set to a true value.

A sig_figs indicates the number of significant figures that should be used when showing the results in the results_table() method. It does not affect the other methods like micro_precision().

add_result($assigned, $correct, $name)

Adds a new result to the experiment. Please see the Statistics::Contingency documentation for a description of this method.

add_hypothesis($hypothesis, $correct_categories)

Adds a new result to the experiment. The first argument is a AI::Categorizer::Hypothesis object such as one generated by a Learner's categorize() method. The list of correct categories can be given as an array of category names (strings), as a hash whose keys are the category names and whose values are anything logically true, or as a single string if there is only one category. For example, all of the following are legal:

 $e->add_hypothesis($h, "sports");
 $e->add_hypothesis($h, ["sports", "finance"]);
 $e->add_hypothesis($h, {sports => 1, finance => 1});

Ken Williams <ken@mathforum.org>

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