File Coverage

blib/lib/Text/NSP/Measures/4D/MI.pm

Criterion	Covered	Total	%
statement	56	170	32.9
branch	38	104	36.5
condition			n/a
subroutine	6	6	100.0
pod	2	2	100.0
total	102	282	36.1

=head1 NAME

Text::NSP::Measures::4D::MI - Perl module that provides error checks and
                              framework to implement Loglikelihood
                              for 4-grams.

=head1 SYNOPSIS

=head3 Basic Usage

  use Text::NSP::Measures::4D::MI::ll;

  $ll_value = calculateStatistic(
                                  n1111=>8,
                                  n1ppp=>306,
                                  np1pp=>83,
                                  npp1p=>83,
                                  nppp1=>57,
                                  n11pp=>8,
                                  n1p1p=>8,
                                  n1pp1=>8,
                                  np11p=>83,
                                  np1p1=>56,
                                  npp11=>56,
                                  n111p=>8,
                                  n11p1=>8,
                                  n1p11=>8,
                                  np111=>56,
                                  npppp=>15180);

  if( ($errorCode = getErrorCode()))
  {
    print STDERR $erroCode." - ".getErrorMessage()."\n";
  }
  else
  {
    print getStatisticName."value for 4-gram is ".$ll_value."\n";
  }

=head1 DESCRIPTION

This module is the base class for the Loglikelihood and the True Mutual
Information measures. All these measure are similar. This module provides
error checks specific for these measures, it also implements the
computations that are common to these measures.

=over

=item Log-Likelihood measure is computed as
 Log-Likelihood = 2 * [n1111 * log ( n1111 / m1111 ) + n1112 * log ( n1112 / m1112 ) +
                       n1121 * log ( n1121 / m1121 ) + n1122 * log ( n1122 / m1122 ) +
                       n1211 * log ( n1211 / m1211 ) + n1212 * log ( n1212 / m1212 ) +
                       n1221 * log ( n1221 / m1221 ) + n1222 * log ( n1222 / m1222 ) +
                       n2111 * log ( n2111 / m2111 ) + n2112 * log ( n2112 / m2112 ) +
                       n2121 * log ( n2121 / m2121 ) + n2122 * log ( n2122 / m2122 ) +
                       n2211 * log ( n2211 / m2211 ) + n2212 * log ( n2212 / m2212 ) +
                       n2221 * log ( n2221 / m2221 ) + n2222 * log ( n2222 / m2222 )];


=back

All these methods use the ratio of the observed values to expected values,
for computations, and thus have common error checks, so they have been grouped
together.

=head2 Methods

=over

=cut


package Text::NSP::Measures::4D::MI;


use Text::NSP::Measures::4D;
use strict;
use Carp;
use warnings;
require Exporter;

our ($VERSION, @EXPORT, @ISA);

@ISA  = qw(Exporter);

@EXPORT = qw(initializeStatistic calculateStatistic
             getErrorCode getErrorMessage getStatisticName
             $n1111 $n1112 $n1121 $n1122 $n1211 $n1212 $n1221 $n1222
	     $n2111 $n2112 $n2121 $n2122 $n2211 $n2212 $n2221 $n2222
             $m1111 $m1112 $m1121 $m1122 $m1211 $m1212 $m1221 $m1222
	     $m2111 $m2112 $m2121 $m2122 $m2211 $m2212 $m2221 $m2222
             $nppp1 $npp1p $npp11 $np1pp $np1p1 $np11p $np111 $n1ppp
             $n1pp1 $n1p1p $n1p11 $n11pp $n11p1 $n111p $npppp
             $nppp2 $npp2p $npp22 $np2pp $np2p2 $np22p $np222 $n2ppp
             $n2pp2 $n2p2p $n2p22 $n22pp $n22p2 $n222p
             $np112 $np121 $np122 $np211 $np212 $np221
             $errorCodeNumber $errorMessage
             getValues computePMI);

$VERSION = '1.03';


=item getValues($count_values) - This method calls
computeMarginalTotals the computeObservedValues() and
the computeExpectedValues() methods to compute the
observed and expected values. It checks these values
for any errors that might cause the Loglikelihood,
TMI and PMI measures to fail.

INPUT PARAMS  : $count_values           .. Reference of an hash containing
                                           the count values computed by the
                                           count.pl program.

RETURN VALUES : 1/undef           ..returns '1' to indicate success
                                    and an undefined(NULL) value to indicate
                                    failure.

=cut

sub getValues
{
  my ($values)=@_;

  if( !(Text::NSP::Measures::4D::computeObservedValues($values)) ) {
      return;
  }

  if( !(Text::NSP::Measures::4D::computeMarginalTotals($values)) ) {
      return;
  }

  if( !(Text::NSP::Measures::4D::computeExpectedValues($values)) ) {
      return;
  }

   # dont want ($n1111 / $m1111) to be 0 or less! flag error if so!
    if ( $n1111 )
    {
	if ($m1111 == 0) {
	    $errorMessage = "Expected value in cell (1,1,1,1) must not be zero";
	    $errorCodeNumber = 231;  return;
	}

	if (($n1111 / $m1111)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,1,1,1)";
	    $errorCodeNumber = 232;  return;
	}
    }

    # dont want ($n1112 / $m1112) to be 0 or less! flag error if so!
    if ( $n1112 )
    {
	if ($m1112 == 0) {
	    $errorMessage = "Expected value in cell (1,1,1,2) must not be zero";
	    $errorCodeNumber = 233;  return;
	}

	if (($n1112 / $m1112)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,1,1,2)";
	    $errorCodeNumber = 234;  return;
	}
    }

    # dont want ($n1121 / $m1121) to be 0 or less! flag error if so!
    if ( $n1121 )
    {
	if ($m1121 == 0) {
	    $errorMessage = "Expected value in cell (1,1,2,1) must not be zero";
	    $errorCodeNumber = 235;  return;
	}

	if (($n1121 / $m1121)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,1,2,1)";
	    $errorCodeNumber = 236;  return;
	}
    }


    # dont want ($n1122 / $m1122) to be 0 or less! flag error if so!
    if ( $n1122 )
    {
	if ($m1122 == 0) {
	    $errorMessage = "Expected value in cell (1,1,2,2) must not be zero";
	    $errorCodeNumber = 237;  return;
	}

	if (($n1122 / $m1122)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,1,2,2)";
	    $errorCodeNumber = 238;  return;
	}
    }

    # dont want ($n1211 / $m1211) to be 0 or less! flag error if so!
    if ( $n1211 )
    {
	if ($m1211 == 0) {
	    $errorMessage = "Expected value in cell (1,2,1,1) must not be zero";
	    $errorCodeNumber = 239;  return;
	}

	if (($n1211 / $m1211)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,2,1,1)";
	    $errorCodeNumber = 240;  return;
	}
    }

    # dont want ($n1212 / $m1212) to be 0 or less! flag error if so!
    if ( $n1212 )
    {
	if ($m1212 == 0) {
	    $errorMessage = "Expected value in cell (1,2,1,2) must not be zero";
	    $errorCodeNumber = 241;  return;
	}

	if (($n1212 / $m1212)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,2,1,2)";
	    $errorCodeNumber = 242;  return;
	}
    }

    # dont want ($n1221 / $m1221) to be 0 or less! flag error if so!
    if ( $n1221 )
    {
	if ($m1221 == 0) {
	    $errorMessage = "Expected value in cell (1,2,2,1) must not be zero";
	    $errorCodeNumber = 243;  return;
	}

	if (($n1221 / $m1221)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,2,2,1)";
	    $errorCodeNumber = 244;  return;
	}
    }

    # dont want ($n1222 / $m1222) to be 0 or less! flag error if so!
    if ( $n1222 )
    {
	if ($m1222 == 0) {
	    $errorMessage = "Expected value in cell (1,2,2,2) must not be zero";
	    $errorCodeNumber = 245;  return;
	}

	if (($n1222 / $m1222)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (1,2,2,2)";
	    $errorCodeNumber = 246;  return;
	}
    }

    # dont want ($n2111 / $m2111) to be 0 or less! flag error if so!
    if ( $n2111 )
    {
	if ($m2111 == 0) {
	    $errorMessage = "Expected value in cell (2,1,1,1) must not be zero";
	    $errorCodeNumber = 247;  return;
	}

	if (($n2111 / $m2111)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,1,1,1)";
	    $errorCodeNumber = 248;  return;
	}
    }

    # dont want ($n2112 / $m2112) to be 0 or less! flag error if so!
    if ( $n2112 )
    {
	if ($m2112 == 0) {
	    $errorMessage = "Expected value in cell (2,1,1,2) must not be zero";
	    $errorCodeNumber = 249;  return;
	}

	if (($n2112 / $m2112)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,1,1,2)";
	    $errorCodeNumber = 250;  return;
	}
    }

    # dont want ($n2121 / $m2121) to be 0 or less! flag error if so!
    if ( $n2121 )
    {
	if ($m2121 == 0) {
	    $errorMessage = "Expected value in cell (2,1,2,1) must not be zero";
	    $errorCodeNumber = 251;  return;
	}

	if (($n2121 / $m2121)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,1,2,1)";
	    $errorCodeNumber = 252;  return;
	}
    }

    # dont want ($n2122 / $m2122) to be 0 or less! flag error if so!
    if ( $n2122 )
    {
	if ($m2122 == 0) {
	    $errorMessage = "Expected value in cell (2,1,2,2) must not be zero";
	    $errorCodeNumber = 253;  return;
	}

	if (($n2122 / $m2122)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,1,2,2)";
	    $errorCodeNumber = 254;  return;
	}
    }

    # dont want ($n2211 / $m2211) to be 0 or less! flag error if so!
    if ( $n2211 )
    {
	if ($m2211 == 0) {
	    $errorMessage = "Expected value in cell (2,2,1,1) must not be zero";
	    $errorCodeNumber = 255;  return;
	}

	if (($n2211 / $m2211)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,2,1,1)";
	    $errorCodeNumber = 256;  return;
	}
    }

    # dont want ($n1111 / $m1111) to be 0 or less! flag error if so!
    if ( $n2212 )
    {
	if ($m2212 == 0) {
	    $errorMessage = "Expected value in cell (2,2,1,2) must not be zero";
	    $errorCodeNumber = 257;  return;
	}

	if (($n2212 / $m2212)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,2,1,2)";
	    $errorCodeNumber = 258;  return;
	}
    }

    # dont want ($n2221 / $m2221) to be 0 or less! flag error if so!
    if ( $n2221 )
    {
	if ($m2221 == 0) {
	    $errorMessage = "Expected value in cell (2,2,2,1) must not be zero";
	    $errorCodeNumber = 259;  return;
	}

	if (($n2221 / $m2221)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,2,2,1)";
	    $errorCodeNumber = 260;  return;
	}
    }

    # dont want ($n2222 / $m2222) to be 0 or less! flag error if so!
    if ( $n2222 )
    {
	if ($m2222 == 0) {
	    $errorMessage = "Expected value in cell (2,2,2,2) must not be zero";
	    $errorCodeNumber = 261;  return;
	}

	if (($n2222 / $m2222)  <= 0) {
	    $errorMessage = "About to take log of negative value for cell (2,2,2,2)";
	    $errorCodeNumber = 262;  return;
	}
    }

  #  Everything looks good so we can return 1
  return 1;
}



=item computePMI($n, $m) - Computes the pmi of a given
observed and expected value pair.

INPUT PARAMS  : $n       ..Observed value
                $m       ..Expected value

RETURN VALUES : lognm   .. the log of the ratio of
                           observed value to expected
                           value.

=cut

sub computePMI
{
    my $n = shift;
    my $m = shift;
    if($n)
    {
	my $val = $n/$m;

	return log($val);
    }
    else
    {
	return 0;
    }
}



1;
__END__