dale-chall-formula

dale-chall-formula

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