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Statistics::Smoothing::SGT - A Simple Good-Turing (SGT) smoothing implementation


Basic Usage

  use Statistics::Smoothing::SGT
  my $sgt = new Statistics::Smoothing::SGT($frequencyClasses, $total);
  $probabilities = $sgt->getProbabilities();
  $newFrequencies = $sgt->getNewFrequencies();
  $nBar = $sgt->getNBar();


Florian Doemges,

Bjoern Wilmsmann,


Copyright (C) 2006, Florian Doemges and Bjoern Wilmsmann, Department of Linguistics, Ruhr-University, Bochum

Partially based on the SGT module (Copyright (C) 2004) by Andre Halama ( and Tibor Kiss (, Department of Linguistics, Ruhr-University, Bochum.

This module in turn was based on the work (including an implementation of the algorithm in C) by Geoffrey Sampson, Department of Informatics, University of Sussex.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to

    The Free Software Foundation, Inc.,
    59 Temple Place - Suite 330,
    Boston, MA  02111-1307, USA.

Note: a copy of the GNU General Public License is available on the web at and is included in this distribution under the name GPL.




This Perl module implements the Simple Good Turing (SGT) algorithm for smoothing of probabilistic values developed by William Gale and Geoffrey Sampson.

The algorithm is described in detail in Sampson's Empirical Linguistics (Continuum International, London and New York, 2001), chapter 7. An online version of this paper is available at Geoffrey Sampson's homepage under

Error Codes


1 POD Error

The following errors were encountered while parsing the POD:

Around line 75:

=over is the last thing in the document?!