The ari_score method calculates the Automated Readability Index (ARI) of a given Essence.Document.

Details

The ARI uses two quantities, mu(w) and mu(s), where mu(w) is average number of letters per word in the given text and mu(s) is the average number of words per sentence in the given text. The ARI is then defined by the following formula: ari = 4.71 * mu(w) + 0.5 * mu(s) - 21.43

Commonly, the ARI score is rounded up and translated by the following table:

Specs

coleman_liau(%Essence.Document{
  meta: term(),
  nested_tokens: term(),
  text: term(),
  type: term(),
  uri: term()
}) :: float()

The Coleman-Liau readability test. Like the ARI but unlike most of the other indices, Coleman–Liau relies on characters instead of syllables per word. Although opinion varies on its accuracy as compared to the syllable/word and complex word indices, characters are more readily and accurately counted by computer programs than are syllables. The Coleman–Liau index was designed to be easily calculated mechanically from samples of hard-copy text. Unlike syllable-based readability indices, it does not require that the character content of words be analyzed, only their length in characters. Therefore, it could be used in conjunction with theoretically simple mechanical scanners that would only need to recognize character, word, and sentence boundaries, removing the need for full optical character recognition or manual keypunching.

The score output approximates the U.S. grade level thought necessary to comprehend the text.

Calculates the Dale-Chall readability score. that provides a numeric gauge of the comprehension difficulty that readers come upon when reading a text. It uses a list of 3000 words that groups of fourth-grade American students could reliably understand, considering any word not on that list to be difficult.

Gunning fog index measures the readability of English writing. The index estimates the years of formal education needed to understand the text on a first reading. A fog index of 12 requires the reading level of a U.S. high school senior (around 18 years old). The test was developed by Robert Gunning, an American businessman, in 1952.[1]

The fog index is commonly used to confirm that text can be read easily by the intended audience. Texts for a wide audience generally need a fog index less than 12. Texts requiring near-universal understanding generally need an index less than 8.

[1] DuBay, William H. (23 March 2004). "Judges Scold Lawyers for Bad Writing". Plain Language At Work Newsletter. Impact Information (8).

Calculates an estimate of the time it would take an average reader to read the given Essence.Document, assuming a reading speed of 200 words per minute.

The smog_grade method calculates the SMOG grade measure of readability that estimates the years of education needed to understand a piece of writing. The SMOG grade is commonly used in rating health messages. Please note that results for documents with less than 30 sentences are statistically invalid[1].

[1] https://en.wikipedia.org/wiki/SMOG

Calculates the speaking speed in words per minute, given a speech described by the given Essence.Document and the recorded speaking_time in minutes.

Calculates an estimate of the time it would take to read the given Essence.Document as a speech, with a speaking speed of 120 words per minute.