Readability metrics

ReadabilityStats(source, sents_extractor=None, words_extractor=None, preset='general')

The readability metrics of a text from its basic statistics: the mean sentence length in words, the mean word length in syllables or letters, the share of polysyllabic and of long words and the variability of word length. The data source is a text, a Doc object of spaCy or ready basic statistics, which are reused as they are; the extractors are passed on to the basic statistics of a text or a Doc. The formulas count only the letters of the counted words, so a word extractor that drops words does not lengthen the mean word.

The metrics are properties computed on each access, so a change of the coefficients of an object applies at once.

Raises:

• SourceTypeError - a source that is neither a string, a Doc nor basic statistics, basic statistics of a class other than those of the library, an extractor of another type, a string or a Doc to a class without basic_stats_class;
• SourceError - a source without words or sentences;
• ParameterError - an unknown preset or one that is not a string.

The metrics assess readability on the side of the language - the complexity of words and syntactic constructions, not the typographic design of the text. They presume that short sentences are easier to read than long ones, long words make reading harder, and low-frequency and unfamiliar words slow a reader down.

The class extends the ReadabilityStats of the anyTS core with the formulas and tables of Spanish, given in the cards of the metrics: the basic statistics of esTS, which take the Spanish SentsExtractor and WordsExtractor by default, the coefficient presets of the Flesch reading ease, the formulas of Gutiérrez de Polini, Crawford and SOL, the consensus grade over Crawford, SOL and the reading ease, the school stages of Spain, the interpretation scales and the reading speeds of Spanish readers. A string with a character without a UTF-8 form, as a file read with the wrong encoding gives, raises SourceError from the Spanish tokenizer.

CodeResult

from ests import ReadabilityStats

text = "Hay tres clases de mentiras: mentiras, malditas mentiras y estadísticas"
rs = ReadabilityStats(text)
rs.print_stats()

                Metric                |  Value
-------------------------------------------------
Flesch reading ease (Szigriszt-Pazos) |  53.55
Gutiérrez de Polini comprehensibility |  33.50
Crawford grade                        |   5.81
Legibilidad µ                         |  50.94
SOL grade (SMOG for Spanish)          |   9.26
LIX readability index                 |  60.00
RIX readability index                 |   5.00
Consensus grade                       |   9.00
Reading time (min)                    |   0.04

Parameters

Parameter	Type	Default	Description
source	str / Doc / BasicStats	-	Data source (a string, a Doc object or ready basic statistics)
sents_extractor	SentsExtractor	None	Sentence extraction tool
words_extractor	WordsExtractor	None	Word extraction tool
preset	str	'general'	Coefficient preset: general or classic

The object keeps the basic statistics of the text in bs, the name of the preset in preset, read-only, and the coefficients of the preset by formula in coefficients, a copy that can be changed for one object. An object of another preset can reuse the basic statistics: ReadabilityStats(rs.bs, preset="classic").

Coefficient presets

A preset sets the coefficients a, b, c of the Flesch reading ease c − a·ASL − b·ASW, where ASL is the mean number of words per sentence and ASW the mean number of syllables per word, and the scale by which describe_level, describe and the consensus grade read it. The other formulas do not depend on the preset.

Preset	Source	Formula	Scale
general	Szigriszt-Pazos (1993), fórmula de perspicuidad	206.835 − 1.0·ASL − 62.3·ASW	INFLESZ (Barrio-Cantalejo et al., 2008)
classic	Fernández Huerta (1959)	206.84 − 1.02·ASL − 60·ASW	the seven bands of the author

The formula of Fernández Huerta takes the mean sentence length, with the correction of Law (2011). The table of all coefficients is ests.constants.READABILITY_PRESETS, and the scale of each preset is in PRESET_SCALES.

CodeResult

classic = ReadabilityStats(rs.bs, preset="classic")
rs.flesch_reading_easy, classic.flesch_reading_easy
rs.describe_level(), classic.describe_level()

(53.545000000000016, 58.640000000000015)
('algo difícil', 'bastante difícil')

Metrics

A formula is computed by the function of its card on the counts of bs. The reading ease takes its coefficients from coefficients, set by the preset; the formulas of Gutiérrez de Polini, Crawford and SOL are computed with the coefficients of their functions, and coefficients does not affect them. A formula of counts gives nan when the number of words or of sentences it divides by is zero. The formulas of other languages, with their own coefficients and no calibration for Spanish, are computed by the UnadaptedReadabilityStats class.

Metric	Measures	Range	Higher means
flesch_reading_easy	Ease of reading by the sentence length and the syllables per word	Nominally 0-100, above 100 for the simplest texts and below 0 for the hardest	An easier text
gutierrez_polini_index	Comprehensibility by the letters per word and the sentence length	Below 95.2, ordinary prose 30-50	An easier text
crawford_grade	Grade by the sentences and the syllables per 100 words	Years of schooling, below 0 for the simplest texts; fitted on grades 1-6	A harder text
mu_index	Mean word length in letters against its variance	Above 0, nan with fewer than two words or without variability	An easier text
sol_grade	Grade by the polysyllabic words per sentence, SMOG converted to Spanish	Years of schooling, slightly below 0 for the simplest texts	A harder text
lix	Sentence length and the share of long words	0 and above	A harder text
rix	Long words per sentence	0 and above	A harder text
consensus_grade	Median of the grade formulas and the reading ease as a grade	Years of schooling	A harder text
reading_time	Reading time at the reading speed (reading_speed)	Minutes, above 0	A longer text
smog_index	Grade by the polysyllabic words per sentence, English coefficients; outside get_stats	Years of schooling	A harder text

The other formulas of the core with their English coefficients - flesch_kincaid_grade, coleman_liau_index, automated_readability_index and gunning_fog_index - are properties of the object outside get_stats as well, since they are fitted on English texts; their cards are on the anyTS page.

Flesch reading ease

flesch_reading_easy · Szigriszt-Pazos, 1993 · Fernández Huerta, 1959

calc_flesch_reading_easy(n_syllables, n_words, n_sents, a=1.0, b=62.3, c=206.835)

The ease of reading a text by the mean sentence length in words and the mean word length in syllables.

\[ c - a \cdot \frac{\textrm{Number of words}}{\textrm{Number of sentences}} - b \cdot \frac{\textrm{Number of syllables}}{\textrm{Number of words}} \]

The default coefficients are those of the fórmula de perspicuidad of Szigriszt-Pazos (1993). The coefficients of Fernández Huerta (1959) are given by the classic preset, with the correction of Law (2011): the last term takes the mean sentence length, not the number of sentences per 100 words that Fernández Huerta printed.

Parameter	Type	Default	Description
n_syllables	int	-	Number of syllables
n_words	int	-	Number of words
n_sents	int	-	Number of sentences
a	float	1.0	Coefficient a, at the mean sentence length
b	float	62.3	Coefficient b, at the mean word length in syllables
c	float	206.835	Coefficient c, the constant

The scale of describe_level and describe follows the preset: the attribute preset_level_scales of the core gives for each preset the scale of ests.constants.READING_EASE_SCALES named in PRESET_SCALES - the INFLESZ scale of Barrio-Cantalejo et al. (2008) for general and the bands of Fernández Huerta for classic; a preset that a subclass adds is read by the scales of general. The INFLESZ scale:

Value	Level	Text type
[80, ∞)	muy fácil	comics, children's books
[65, 80)	bastante fácil	primary school textbooks
[55, 65)	normal	general press
[40, 55)	algo difícil	secondary school textbooks
(−∞, 40)	muy difícil	scientific and technical texts

flesch_reading_easy_to_level(flesch_reading_easy, scale='inflesz')

The band of a scale of READING_EASE_SCALES for the reading ease: inflesz (above), szigriszt (Szigriszt-Pazos, 1993, integer bands: muy difícil 0-15, árido 16-35, bastante difícil 36-50, normal 51-65, bastante fácil 66-75, fácil 76-85, muy fácil 86-100) and fernandez_huerta (Fernández Huerta, 1959: muy difícil below 30, difícil 30-50, bastante difícil 50-60, normal 60-70, bastante fácil 70-80, fácil 80-90, muy fácil above 90). The describe_level method reads the reading ease of the object by any of them with its scale parameter.

Parameter	Type	Default	Description
flesch_reading_easy	float	-	Value of the reading ease
scale	str	'inflesz'	Name of the scale: inflesz, szigriszt or fernandez_huerta

Raises:

• ParameterError - an unknown scale or one that is not a string, a value that is not a finite number.

CodeResult

from ests.readability_stats import flesch_reading_easy_to_level

flesch_reading_easy_to_level(53.5), flesch_reading_easy_to_level(53.5, "szigriszt")

('algo difícil', 'normal')

Sources: Szigriszt Pazos, F. Sistemas predictivos de legibilidad del mensaje escrito: fórmula de perspicuidad. Universidad Complutense de Madrid, 1993. Barrio-Cantalejo, I. M. et al. Validación de la Escala INFLESZ para evaluar la legibilidad de los textos dirigidos a pacientes. Anales del Sistema Sanitario de Navarra, 31(2), 2008. Fernández Huerta, J. Medidas sencillas de lecturabilidad. Consigna, 214, 1959. Law, G. Error in the Fernández Huerta readability formula. LINGUIST List 22.2332, 2011.

Gutiérrez de Polini comprehensibility

gutierrez_polini_index · Gutiérrez de Polini, 1972

calc_gutierrez_polini_index(n_letters, n_words, n_sents)

The fórmula de comprensibilidad of Gutiérrez de Polini, by the mean word length in letters and the mean sentence length. The higher the value, the easier the text. It was fitted on sixth-grade school texts and has no scale of its own: ordinary prose lies between 30 and 50, and a text above 70 is read by a young child.

\[ 95.2 - 9.7 \cdot \frac{\textrm{Number of letters}}{\textrm{Number of words}} - 0.35 \cdot \frac{\textrm{Number of words}}{\textrm{Number of sentences}} \]

Parameter	Type	Default	Description
n_letters	int	-	Number of letters of the words
n_words	int	-	Number of words
n_sents	int	-	Number of sentences

CodeResult

from ests.readability_stats import calc_gutierrez_polini_index

calc_gutierrez_polini_index(n_letters=60, n_words=10, n_sents=1)

33.5

Source: Gutiérrez de Polini, L. E. Investigación sobre lectura en Venezuela. Ministerio de Educación, Caracas, 1972.

Crawford grade

crawford_grade · Crawford, 1989

calc_crawford_grade(n_syllables, n_words, n_sents)

The years of schooling needed to read the text, by the sentences and the syllables per 100 words. The formula was fitted on Spanish primary school readers of grades 1-6, so higher values saturate. The higher the value, the harder the text.

\[ -0.205 \cdot \frac{100 \cdot \textrm{Number of sentences}}{\textrm{Number of words}} + 0.049 \cdot \frac{100 \cdot \textrm{Number of syllables}}{\textrm{Number of words}} - 3.407 \]

Parameter	Type	Default	Description
n_syllables	int	-	Number of syllables
n_words	int	-	Number of words
n_sents	int	-	Number of sentences

CodeResult

from ests.readability_stats import calc_crawford_grade

calc_crawford_grade(n_syllables=23, n_words=10, n_sents=1)

5.812999999999999

Source: Crawford, A. N. Fórmula y gráfico para determinar la comprensibilidad de textos del nivel primario en castellano. Lectura y Vida, 10(4), 1989.

Legibilidad µ

mu_index · Muñoz Baquedano and Muñoz Urra, 2006

calc_mu_index(c_letters)

The mean number of letters per word divided by its sample variance, times 100; there are no coefficients to fit. Words without letters (numbers) are left out; with fewer than two words or without variability the index is undefined (nan).

\[ 100 \cdot \frac{\bar{x}}{s^2}, \quad s^2 = \frac{\sum (x_i - \bar{x})^2}{n - 1} \]

where \(x_i\) is the number of letters of a word and \(n\) the number of words.

Parameter	Type	Default	Description
c_letters	dict[int, int]	-	Distribution of words by number of letters

A c_letters that is not a mapping raises SourceTypeError.

The variance divided by n − 1 is the cuasivarianza of the authors, which reproduces the worked example of their manual; ReadabilityStats passes BasicStats.c_letters. The bands of the authors, ests.constants.MU_SCALE, are the scale of describe_level and describe:

Value	Level
[91, ∞)	muy fácil
[81, 91)	fácil
[71, 81)	un poco fácil
[61, 71)	adecuado
[51, 61)	un poco difícil
[31, 51)	difícil
(−∞, 31)	muy difícil

mu_to_level(mu_index)

The band of the scale MU_SCALE for a value of Legibilidad µ.

Parameter	Type	Default	Description
mu_index	float	-	Value of Legibilidad µ

Raises:

• ParameterError - a value that is not a finite number, such as the undefined index (nan).

CodeResult

from ests import BasicStats
from ests.readability_stats import calc_mu_index, mu_to_level

mu = calc_mu_index(BasicStats(text).c_letters)
mu, mu_to_level(mu)

(50.943396226415096, 'difícil')

Source: Muñoz Baquedano, M. Legibilidad y variabilidad de los textos. Boletín de Investigación Educacional, 21(2), 2006; the program and manual at legibilidadmu.cl.

SOL grade

sol_grade · Contreras et al., 1999

calc_sol_grade(n_complex, n_sents, a=0.74, b=-2.51)

The years of schooling needed to read a Spanish text: the conversion of Contreras et al. of its SMOG index S, computed with the original coefficients, into the grade of the English scale. The higher the value, the harder the text. ReadabilityStats passes the number of words of three or more syllables.

\[ b + a \cdot S \]

Parameter	Type	Default	Description
n_complex	int	-	Number of words of three or more syllables
n_sents	int	-	Number of sentences
a	float	0.74	Coefficient a, at the SMOG index
b	float	-2.51	Coefficient b, the constant

Raises:

• ParameterError - a number of words or sentences that is not a non-negative integer.

CodeResult

from ests.readability_stats import calc_smog_index, calc_sol_grade

calc_smog_index(n_complex=5, n_sents=1), calc_sol_grade(n_complex=5, n_sents=1)

(15.903189008614273, 9.258359866374562)

Source: Contreras, A., García-Alonso, R., Echenique, M., Daye-Contreras, F. The SOL formulas for converting SMOG readability scores between health education materials written in Spanish, English, and French. Journal of Health Communication, 4(1), 1999.

LIX readability index

lix · Björnsson, 1968

calc_lix(n_long_words, n_words, n_sents)

The mean sentence length plus the percentage of long words, the words of more than six letters; there are no coefficients to fit. The values read as text types:

Value	Text
0-30	very easy texts, children's books
30-40	easy texts, fiction, newspaper articles
40-50	texts of medium difficulty, magazine articles
50-60	hard texts, popular science, official texts
60-100	very hard texts, laws and bureaucratic language

\[ \frac{\textrm{Number of words}}{\textrm{Number of sentences}} + \frac{100 \cdot \textrm{Number of long words}}{\textrm{Number of words}} \]

Parameter	Type	Default	Description
n_long_words	int	-	Number of long words
n_words	int	-	Number of words
n_sents	int	-	Number of sentences

These bands, anyts.constants.LIX_LEVELS with English labels, are the scale of describe_level and describe; its last band is open above.

RIX readability index

rix · Anderson, 1983

calc_rix(n_long_words, n_sents)

The long words, of more than six letters, per sentence; there are no coefficients to fit. The values read as grades:

Value	Grade
< 0.2	1
0.2-0.5	2
0.5-0.8	3
0.8-1.3	4
1.3-1.8	5
1.8-2.4	6
2.4-3.0	7
3.0-3.7	8
3.7-4.5	9
4.5-5.3	10
5.3-6.2	11
6.2-7.2	12
> 7.2	college

\[ \frac{\textrm{Number of long words}}{\textrm{Number of sentences}} \]

Parameter	Type	Default	Description
n_long_words	int	-	Number of long words
n_sents	int	-	Number of sentences

In esTS RIX has no scale of bands, so describe_level("rix") raises ParameterError; describe takes the grades of Anderson as years of schooling (anyts.constants.RIX_GRADES, college as 13) and gives the stage of the Spanish school system and the reader age by grade_to_age.

Consensus grade

consensus_grade

The consensus_grade attribute is the median of the values of the grade formulas (grade_stats) rounded half up, together with the reading ease in years of schooling (reading_ease_to_grade), not rounded. A library aligns the bounds of reading_ease_grades, and of each scale of preset_reading_ease_grades, with its scale of the reading ease, so that the consensus grade and describe read the value alike.

The grade formulas of esTS (ests.constants.READABILITY_GRADE_STATS) are Crawford and SOL. esTS converts the reading ease into years of schooling by the scale of the preset: the attribute preset_reading_ease_grades of the core gives for each preset the bounds of READING_EASE_GRADES and 13 below them, the scale of flesch_reading_easy_to_grade, so the reading_ease_grades of the core are not used.

Warning

Crawford was fitted on primary school readers and saturates for adult texts; SOL was fitted on health education materials. The consensus grade of a technical text mostly reflects the reading ease band.

calc_consensus_grade(grades, flesch_reading_easy=None, preset='general')

The median of the values of the grade formulas rounded half up, together with the reading ease converted into years of schooling by flesch_reading_easy_to_grade with the scale of the preset, not rounded.

\[ \textrm{median}\left(\lfloor g_1 + 0.5 \rfloor, \ldots, \lfloor g_k + 0.5 \rfloor, \textrm{grade}(\textrm{reading ease})\right) \]

Parameter	Type	Default	Description
grades	list[float]	-	Values of the grade formulas
flesch_reading_easy	float	None	Value of the reading ease
preset	str	'general'	Coefficient preset of the reading ease

Raises:

• ParameterError - no values at all, a grade or a reading ease that is not a finite number, an unknown preset or one that is not a string;
• SourceTypeError - grades that are not a list.

flesch_reading_easy_to_grade(flesch_reading_easy, preset='general')

Conversion of the Flesch reading ease into years of schooling for the consensus grade by the bands of the scale of the preset, ests.constants.READING_EASE_GRADES: the grade of the first band whose lower bound the value reaches, or 13 below the last bound; values above 100 belong to the first band. With the general preset, through the text types of the INFLESZ bands and the school stages of Spain:

Reading ease	Grade	Text type
[80, ∞)	3	comics and children's books, primary school grades 1-3
[65, 80)	5	primary school textbooks, grades 4-6
[55, 65)	8	general press, ESO
[40, 55)	11	secondary school textbooks, bachillerato
(−∞, 40)	13	scientific texts, university

With the classic preset, through the interpretation table of Flesch kept by Fernández Huerta: 90-100 - 5, 80-90 - 6, 70-80 - 7, 60-70 - 8.5, 50-60 - 10, 40-50 - 11, 30-40 - 12, below 30 - 13.

Parameter	Type	Default	Description
flesch_reading_easy	float	-	Value of the reading ease
preset	str	'general'	Coefficient preset whose scale is read

Raises:

• ParameterError - a reading ease that is not a finite number (the nan of a text without words or sentences, an infinity), an unknown preset or one that is not a string.

CodeResult

from ests.readability_stats import calc_consensus_grade, flesch_reading_easy_to_grade

flesch_reading_easy_to_grade(53.545), flesch_reading_easy_to_grade(53.545, "classic")
calc_consensus_grade([5.813, 9.258], 53.545)

(11, 10)
9.0

Reading time

reading_time · reading_time_by_speed(wpm) · reading_time_by_norm(norm) · Brysbaert, 2019 · Ripoll, Tapia and Aguado, 2020

calc_reading_time(n_words, wpm=278)

The reading time of a text in minutes: the number of words divided by the reading speed.

\[ \frac{\textrm{Number of words}}{\textrm{wpm}} \]

A number of words that is not a non-negative integer and a speed that is not a positive number raise ParameterError.

The default speed is the silent reading speed of adults in Spanish, 278 words per minute, from the meta-analysis of Brysbaert (2019). The norms of reading_time_by_norm, ests.constants.READING_SPEED_NORMS, are the mean speeds of Spanish-speaking students by school year from the meta-analysis of Ripoll, Tapia and Aguado (2020) - grade_1 to grade_11, that is primary school 1-6, ESO 7-10 and bachillerato 11 - and of adults from Brysbaert (2019), as pairs (aloud, silent):

Norm	Aloud	Silent
grade_1	49	30
grade_2	73	79
grade_3	85	95
grade_4	104	125
grade_5	114	137
grade_6	124	155
grade_7	134	180
grade_8	136	176
grade_9	143	180
grade_10	164	200
grade_11	161	186
adult	191	278

Parameter	Type	Default	Description
n_words	int	-	Number of words
wpm	float	278	Reading speed, words per minute (READING_SPEED_WPM)

Sources: Brysbaert, M. How many words do we read per minute? A review and meta-analysis of reading rate. Journal of Memory and Language, 109, 2019. Ripoll, J. C., Tapia, M. M., Aguado, G. Velocidad lectora en alumnado hispanohablante: un metaanálisis. Revista de Psicodidáctica, 25(2), 2020.

SMOG index

smog_index · McLaughlin, 1969

calc_smog_index(n_complex, n_sents, a=1.043, b=30, c=3.1291)

The years of schooling needed to read the text, by the polysyllabic words per sentence. In the original formula the polysyllabic words have three or more syllables and b brings their number to a sample of 30 sentences.

\[ a \cdot \sqrt{b \cdot \frac{\textrm{Number of polysyllabic words}}{\textrm{Number of sentences}}} + c \]

A number of words or sentences that is not a non-negative integer raises ParameterError.

The index is fitted on English and stays outside get_stats; for Spanish it is the input of the SOL grade. ReadabilityStats passes the number of words of three or more syllables.

Parameter	Type	Default	Description
n_complex	int	-	Number of polysyllabic words
n_sents	int	-	Number of sentences
a	float	1.043	Coefficient a, at the square root
b	float	30	Coefficient b, the number of sentences of the sample
c	float	3.1291	Coefficient c, the constant

Methods

describe_grade(stat) returns the school stage and reader age for the consensus grade or the grade formula stat, consensus_grade by default; another metric raises ParameterError.

The grade formulas of esTS are crawford_grade and sol_grade.

describe_level(stat) returns the band of the interpretation scale (level_scale) of the metric stat, flesch_reading_easy by default; a metric without a scale of bands and an undefined value (nan) raise ParameterError.

In esTS the metrics with a scale of bands are flesch_reading_easy, mu_index and lix, and describe_level(stat, scale) also takes a scale of READING_EASE_SCALES for the reading ease - inflesz, szigriszt or fernandez_huerta - in place of the scale of the preset, None by default; a scale given for another metric and an unknown scale raise ParameterError. level_scale(stat) returns the scale of a metric as lower bounds and their bands - for the reading ease the scale of the preset - or None for a metric without a scale of bands, RIX included.

describe(stat) returns the reading of any metric by its scale: for the consensus grade and a grade formula the school stage and reader age (describe_grade), for a metric with a scale of bands (level_scale) its band, for another metric of grade_scales the stage and age of the years of schooling its scale gives, and None for a metric without a scale or with an undefined value (nan). A name that is neither in stats_desc nor a public property of the class raises UnknownStatError.

In esTS the grade formulas are read as stages of the Spanish school system, and so is RIX through the grades of Anderson; the formula of Gutiérrez de Polini, the reading time and the formulas of the core with their English coefficients have no scale.

reading_time_by_speed(wpm) returns the reading time of the text in minutes at the speed wpm, words per minute; a speed that is not a positive number raises ParameterError.

reading_time_by_norm(norm) returns the reading times of the text in minutes at the speeds of the norm norm of reading_speed_norms, in their order; an unknown norm raises ParameterError.

The norms of esTS give the speeds aloud and silently, so the method returns the reading times aloud and silently.

get_stats() returns a dictionary of the readability metrics of stats_desc.

print_stats() prints a table of the readability metrics with their descriptions from stats_desc under the headers of stats_headers.

CodeResult

rs.describe_grade(), rs.describe_grade("crawford_grade")
rs.describe_level(scale="szigriszt"), rs.describe_level("mu_index")
rs.level_scale("flesch_reading_easy")
rs.reading_time_by_speed(200), rs.reading_time_by_norm("grade_4")
{stat: rs.describe(stat) for stat in rs.get_stats()}
rs.get_stats()

('ESO (12-16 years)', 'primary school, grades 4-6 (9-12 years)')
('normal', 'difícil')
((80, 'muy fácil'),
 (65, 'bastante fácil'),
 (55, 'normal'),
 (40, 'algo difícil'),
 (0, 'muy difícil'))
(0.05, (0.09615384615384616, 0.08))
{'flesch_reading_easy': 'algo difícil',
 'gutierrez_polini_index': None,
 'crawford_grade': 'primary school, grades 4-6 (9-12 years)',
 'mu_index': 'difícil',
 'sol_grade': 'ESO (12-16 years)',
 'lix': 'very hard texts, laws and bureaucratic language',
 'rix': 'ESO (12-16 years)',
 'consensus_grade': 'ESO (12-16 years)',
 'reading_time': None}
{'flesch_reading_easy': 53.545000000000016,
 'gutierrez_polini_index': 33.5,
 'crawford_grade': 5.812999999999999,
 'mu_index': 50.943396226415096,
 'sol_grade': 9.258359866374562,
 'lix': 60.0,
 'rix': 5.0,
 'consensus_grade': 9.0,
 'reading_time': 0.03597122302158273}

The to_dataframe method is that of the statistics interface of the anyTS core.

Scales

The describe_level method reads the reading ease, Legibilidad µ and LIX by the scales of bands of their cards, and describe reads any metric: these three by the same scales, the grade formulas, the consensus grade and RIX by the school stages of grade_to_age; for a metric without a scale it gives None.

School stage and age

grade_to_age(grade)

The stage of the Spanish school system and the reader age by the value of a grade formula, in years of schooling counted from the first year of primary school at the age of six: the value is rounded half up and falls into the first stage whose last year it does not exceed, values below 1 into grades 1-3. The stages are ests.constants.GRADE_AGE_LEVELS and POSTGRADUATE_LEVEL:

Grade	Stage	Age
1-3	primary school, grades 1-3	6-9 years
4-6	primary school, grades 4-6	9-12 years
7-10	ESO	12-16 years
11-12	bachillerato	16-18 years
13-16	university	18-22 years
above 16	postgraduate	over 22 years

Parameter	Type	Default	Description
grade	float	-	Value of a grade formula

Raises:

• ParameterError - a grade that is not a finite number.

CodeResult

from ests.readability_stats import grade_to_age

grade_to_age(9.0), grade_to_age(17)

('ESO (12-16 years)', 'postgraduate (over 22 years)')

Band of a scale

scale_level(value, scale)

The band of a scale for a value: the scale is given as the lower bounds of its bands in descending order, the value falls into the first band whose bound it reaches, and the lowest band is open below.

Parameter	Type	Default	Description
value	float	-	Value of a metric
scale	list[tuple[float, Any]]	-	Lower bounds and their bands in descending order

A value that is not a finite number and a scale that is empty, not a list of pairs of a finite lower bound and a band or with bounds that do not descend raise ParameterError.

The scales of esTS are READING_EASE_SCALES and MU_SCALE of ests.constants; LIX is read by the LIX_LEVELS of the core.

CodeResult

from ests.constants import MU_SCALE, READING_EASE_SCALES
from ests.readability_stats import scale_level

scale_level(50.9, MU_SCALE), scale_level(50.9, READING_EASE_SCALES["fernandez_huerta"])

('difícil', 'bastante difícil')