text-scorer

text-scorer (v2.0.0)

A configurable text quality scorer/gibberish detector.

Installation

npm install text-scorer

Description and Use Cases

This text scoring model implements a matrix that tracks the probabilities of character bigram and trigram transitions, i.e. a Markov chain where the event chains consist of character bigrams and trigrams and the transition probabilities correspond to approximate relative frequencies of each chain within the English language. The model consists of three major parts:

1. English language training. A large corpus (for example, the default training text is a Harry Potter novel) is passed to the model to learn the relative frequencies of all character N-grams. For example, the model will learn through training that the t-h bigram is much more likely to occur than the q-g bigram.
2. Cutoff training. A sample of good and bad inputs is passed to the model so that it can calculate predictions for what the cutoff point between gibberish and non-gibberish will be.
3. Input/output. Inputs passed to the trained model will be evaluated and assigned a score (the average of all character N-gram probabilities in the input). That score is compared against the model's cutoff predictions to come up with the final predictions.

Sample use cases:

• Filter gibberish spam from list of tweets, emails, survey responses, etc.
• Check if the input to a text field or a form is gibberish
• Remove nonsensical tokens from tokenized text input

Usage and Examples

Import module

import { TextScorer } from 'text-scorer'
import { CutoffScoreStrictness, NGramMatrix } from 'text-scorer' // Additional type imports

Constructor

const textScorer = new TextScorer(useBigram?: boolean, options?: {
    initialTrainingText?: string
    goodSamples?: string[]
    badSamples?: string[]
    ignoreCase?: boolean
    additionalCharsToInclude?: string
})

Instantiates new TextScorer object. Constructor takes optional arguments useBigram (defaults to true, which prefers bigrams over trigrams) and options:

options field	type	purpose/description	default value
initialTrainingText	string	An English corpus/text in string format to initialize N-gram probability matrix	stringified Harry Potter & the Sorcerer's Stone
goodSamples	string[]	An array of manually selected correctly-spelled English sentences to calculate predicted cutoff scores in conjunction with badSamples	hard-coded array of English sentence strings
badSamples	string[]	An array of gibberish strings to calculate predicted cutoff scores in conjunction with goodSamples	hard-coded array of gibberish strings
ignoreCase	boolean	If true, converts all training input text and scoring output text to lower case. Else, considers upper lower case chars in N-grams	true
additionalCharsToInclude	string	All unique chars in additionalCharsToInclude are appended to the base set of chars ([a-z] and space, or unicodes 97-122 and 32) to include in N-grams.	''

isGibberish

textScorer.isGibberish('The quick fox jumps over the lazy dog') // false
textScorer.isGibberish('Tom Brady') // false
textScorer.isGibberish('oqbwifsiehf osdfbw sjkdoo thehwei') // true
textScorer.isGibberish('This sentence is half gibberish lwpqgtyukcvi', CutoffScoreStrictness.Loose) // false
textScorer.isGibberish('This sentence is half gibberish lwpqgtyukcvi', CutoffScoreStrictness.Strict) // true

Returns whether input text string is gibberish, according to trained cutoff predictions and desired strictness. strictness argument must be of a member of the CutoffScoreStrictness enum (Strict | Avg | Loose), where CutoffScoreStrictness.Strict will classify more input strings as gibberish and CutoffScoreStrictness.Loose will classify fewer input strings as gibberish. The strictness argument defaults to Avg.

trainWithEnglishText

textScorer.trainWithEnglishText(my_own_training_text) // Additional training for textScorer if desired

Trains the TextScorer object with any training string passed to it. This will re-adjust the N-gram probabilities on top of the initial training and any prior training. Training also automatically recalibrates cutoff score predictions. Recommended to train only on long training corpus in accurate English.

recalibrateCutoffScores

textScorer.recalibrateCutoffScores(good_sample_texts, bad_sample_texts) // Recalculate predicted score cutoffs based on provided samples

Manually re-calibrate the estimated cutoff scores. Takes parameters of two hand-picked string[] of good and bad sample texts.

getTextScore

textScorer.getTextScore('The quick fox jumps over the lazy dog') // 0.07108346875540186
textScorer.getTextScore('asdk akljhsug wertgbk') // 0.009196665505633908

Returns actual calculated number score of input text (average probability of all N-grams in input text: range between 0 and 1 with avg 1/26 for bigrams and 1/(26*26) = 1/676 for trigrams). Useful for viewing scores of input texts to choose your own hard-coded cutoff score points.

getCutoffScores

textScorer.getCutoffScores()
// {
//    loose: 0.017614231370230753,
//    avg: 0.025681000339544513,
//    strict: 0.033747769308858276
//  },

Returns predicted cutoff scores at all three strictness levels (loose, avg, and strict).

getTextScoreAndCutoffs

textScorer.getTextScoreAndCutoffs('This sentence is half gibberish lwpqgtyukcvi')
// {
//   cutoffs: {
//     loose: 0.017614231370230753,
//     avg: 0.025681000339544513,
//     strict: 0.033747769308858276
//   },
//   score: 0.029883897109006206
// }

Returns current predicted cutoff scores of NGramMatrix bundled together with the calculated numerical score of input text for further inspection.

Type and enum definitions

interface TextScorerInterface {
    NGramMatrix: NGramMatrix
    trainWithEnglishText: (text: string) => void
    recalibrateScoreCutoffs: (goodSamples: string[], badSamples: string[]) => void
    isGibberish: (text: string, strictness?: CutoffScoreStrictness) => boolean
    getTextScore: (text: string) => number
    getScoreCutoffs: () => CutoffScore
    getTextScoreAndCutoffs: (text: string) => { cutoffs: CutoffScore; score: number }
}

class TextScorer implements TextScorerInterface {}

interface NGramMatrix {
    cutoffScores: CutoffScore
    train: (text: string) => void
    getScore: (text: string) => number
    recalibrateCutoffScores: (goodSamples?: string[], badSamples?: string[]) => void
    isGibberish: (text: string, strictness?: CutoffScoreStrictness) => boolean
}

interface NGramMatrixOptions {
    initialTrainingText?: string
    goodSamples?: string[]
    badSamples?: string[]
    ignoreCase?: boolean
    additionalCharsToInclude?: string
}

enum CutoffScoreStrictness {
    Strict = 'Strict',
    Avg = 'Avg',
    Loose = 'Loose',
}

License

MIT