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) 2011 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.