Formula to detect the grade level of text according to the (revised) Dale–Chall Readability Formula (1995)
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dale-chall-formula Build Status Coverage Status

Formula to detect the grade level of text according to the (revised) Dale–Chall Readability Formula.

See dale-chall for a list of words which count as “familiar”.

Installation

npm:

npm install dale-chall-formula

Usage

var daleChallFormula = require('dale-chall-formula')

daleChallFormula({word: 30, sentence: 2, difficultWord: 6}) // => 4.41208

daleChallFormula({word: 30, sentence: 2}) // => 0.744

daleChallFormula() // => NaN

daleChallFormula.gradeLevel(daleChallFormula(30, 2, 6)) // => [9, 10]

API

daleChallFormula(counts)

Given the number of words (word), the number of sentences (sentence), and the number of unique unfamiliar words in a document (difficultWord), returns the score associated with the document.

daleChallFormula.gradeLevel(score)

Given a score, returns the corresponding grade ranges

Score Corresponding Grade Level Return value
Less than 5 Grade 4 and lower [0, 4]
Less than 6 Grades 5 and 6 [5, 6]
Less than 7 Grades 7 and 8 [7, 8]
Less than 8 Grades 9 and 10 [9, 10]
Less than 9 Grades 11 and 12 [11, 12]
Less than 10 Grades 13 and 15 (College) [13, 15]
Higher Grades 16 and higher (College Graduate) [16, Infinity]

Related

  • automated-readability — Uses character count instead of error-prone syllable parser
  • coleman-liau — Uses letter count instead of an error-prone syllable parser
  • flesch — Uses syllable count
  • flesch-kincaid — Like flesch-formula, returns U.S. grade levels
  • gunning-fog — Uses syllable count, needs POS-tagging and NER
  • smog-formula — Like gunning-fog-index, without needing advanced NLP
  • spache-formula — Uses a dictionary, suited for lower reading levels

License

MIT © Titus Wormer