Lingua::EN::Fathom(3p)

NAME
Lingua::EN::Fathom - Measure readability of English text

SYNOPSIS
    use Lingua::EN::Fathom;

    my $text = new Lingua::EN::Fathom;

    $text->analyse_file("sample.txt");

    $accumulate = 1;
    $text->analyse_block($text_string,$accumulate);

    $num_chars             = $text->num_chars;
    $num_words             = $text->num_words;
    $percent_complex_words = $text->percent_complex_words;
    $num_sentences         = $text->num_sentences;
    $num_text_lines        = $text->num_text_lines;
    $num_blank_lines       = $text->num_blank_lines;
    $num_paragraphs        = $text->num_paragraphs;
    $syllables_per_word    = $text->syllables_per_word;
    $words_per_sentence    = $text->words_per_sentence;

    %words = $text->unique_words;
    foreach $word ( sort keys %words )
    {
      print("$words{$word} :$word\n");
    }

    $fog     = $text->fog;
    $flesch  = $text->flesch;
    $kincaid = $text->kincaid;

    print($text->report);

REQUIRES
Perl, version 5.001 or higher, Lingua::EN::Syllable

DESCRIPTION
This module analyses English text in either a string or file. Totals are then calculated for the number of characters, words, sentences, blank and non blank (text) lines and paragraphs.

Three common readability statistics are also derived, the Fog, Flesch and Kincaid indices.

All of these properties can be accessed through individual methods, or by generating a text report.

A hash of all unique words and the number of times they occur is generated.

METHODS

  new
The "new" method creates an instance of an text object This must be called before any of the following methods are invoked. Note that the object only needs to be created once, and can be reused with new input data.

   my $text = new Lingua::EN::Fathom;

  analyse_file
The "analyse_file" method takes as input the name of a text file. Various text based statistics are calculated for the file. This method and "analyse_block" are prerequisites for all the following methods. An optional argument may be supplied to control accumulation of statistics. If set to a non zero value, all statistics are accumulated with each successive call.

    $text->analyse_file("sample.txt");

  analyse_block
The "analyse_block" method takes as input the name of a text file. Various text based statistics are calculated for the file. This method and "analyse_file" are prerequisites for all the following methods. An optional argument may be supplied to control accumulation of statistics. If set to a non zero value, all statistics are accumulated with each successive call.

    $text->analyse_block("sample.txt");

  num_chars
Returns the number of characters in the analysed text file or block. This includes characters such as spaces, and punctuation marks.

  num_words
Returns the number of words in the analysed text file or block. A word must consist of letters a-z with at least one vowel sound, and optionally an apostrophe or hyphen. Items such as "&, K108, NW" are not counted as words.

  percent_complex_words
Returns the percentage of complex words in the analysed text file or block. A complex word must consist of three or more syllables. This statistic is used to calculate the fog index.

  num_sentences
Returns the number of sentences in the analysed text file or block. A sentence is any group of words and non words terminated with a single full stop. Spaces may occur before and after the full stop.

  num_text_lines
Returns the number of lines containing some text in the analysed text file or block.

  num_blank_lines
Returns the number of lines NOT containing any text in the analysed text file or block.

  num_paragraphs
Returns the number of paragraphs in the analysed text file or block.

  syllables_per_word
Returns the average number of syllables per word in the analysed text file or block.

  words_per_sentence
Returns the average number of words per sentence in the analysed text file or block.

  READABILITY
Three indices of text readability are calculated. They all measure complexity as a function of syllables per word and words per sentence. They assume the text is well formed and logical. You could analyse a passage of nonsensical English and find the readability is quite good, provided the words are not too complex and the sentences not too long.

For more information see: <http://www.plainlanguage.com/Resources/readability.html>

  fog
Returns the Fog index for the analysed text file or block.

  ( words_per_sentence + percent_complex_words ) * 0.4

The Fog index, developed by Robert Gunning, is a well known and simple formula for measuring readability. The index indicates the number of years of formal education a reader of average intelligence would need to read the text once and understand that piece of writing with its word sentence workload.

   18 unreadable
   14 difficult
   12 ideal
   10 acceptable
    8 childish

  flesch
Returns the Flesch reading ease score for the analysed text file or block.

   206.835 - (1.015 * words_per_sentence) - (84.6 * syllables_per_word)

This score rates text on a 100 point scale. The higher the score, the easier it is to understand the text. A score of 60 to 70 is considered to be optimal.

  kincaid
Returns the Flesch-Kincaid grade level score for the analysed text file or block.

   (11.8 * syllables_per_word) +  (0.39 * words_per_sentence) - 15.59;

This score rates text on U.S. grade school level. So a score of 8.0 means that the document can be understood by an eighth grader. A score of 7.0 to 8.0 is considered to be optimal.

  unique_words
Returns a hash of unique words. The words (in lower case) are held in the hash keys while the number of occurrences are held in the hash values.

  report
    print($text->report);

Produces a text based report containing all Fathom statistics for the currently analysed text block or file. For example:

Number of characters : 813 Number of words : 135 Percent of complex words : 20.00 Average syllables per word : 1.7704 Number of sentences : 12 Average words per sentence : 11.2500 Number of text lines : 13 Number of blank lines : 8 Number of paragraphs : 4

READABILITY INDICES

Fog : 12.5000 Flesch : 45.6429 Flesch-Kincaid : 9.6879

The return value is a string containing the report contents

SEE ALSO
Lingua::EN::Syllable,Lingua::EN::Sentence,B::Fathom

POSSIBLE EXTENSIONS
   Count white space and punctuation characters
   Allow user control over what strictly defines a word
   Provide a density measure of white space to characters

LIMITATIONS
The syllable count provided in Lingua::EN::Syllable is about 90% accurate

Acronyms that contain vowels, like GPO, will be counted as words.

The fog index should exclude proper names

BUGS
None known

AUTHOR
Lingua::EN::Fathom was written by Kim Ryan <kimryan at cpan dot org>.

COPYRIGHT AND LICENSE
Copyright (c) 2007 Kim Ryan. All rights reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.4 or, at your option, any later version of Perl 5 you may have available.