A Machine-Learning project for detection of langage and spelling correction.
How it works
A misspelled word can be considered as the observation of the real word that was meant to be written. Thus, correcting a spelling mistake is a classification problem of finding the correct class among all the existing words of a language. In this project, a Naive Bayes Classifier has been implemented.
Here's how it works: if,
mis the word typed by the user
cis a possible correction of this word
P(c|m)is the probability that a user who typed
mactually meant to type a correct word
The Bayes Formula states that:
P(c|m) = P(m|c)*P(c)/P(m)
We want to find
c that maximizes
P(c|m), so we can ignore
P(m) (which is constant) and maximize
P(m|c)is the probability of making the mistake
mby meaning to type
c. It is the error model.
P(c)is the probability that the user wanted to type
c. It is the language model.
To model the typing errors, we use the editing distance
d(m,c), which is the number of elementary operations (deletion, insetion, replacement or transposition of letters) needed to move from
The error model can be written
P(m|c) = Pe^d(m,c), with
Pe a fixed error probability for mistyping one letter.
To model the probability of a given word to appear in a text, we can use pragmatic approach: the more this word appears in a large corpus, the greater its probability.
The language model
P(c) is the frequency of the word c in the corpus.
Finally, for any given typed word
m, we generate a lot of potential correction canditates by generating errors of editing distance <= 2. Then, for each of this candidate words we compute the probability P(c|m) that they are the right correction, and we select the candidate with the highest probability.
The same approach can be used to determine the language of the sentence.
I used the following corpus for training the language models.
|Émile Zola, L'argent||William Shakespeare, Henry VI|
|Émile Zola, L'assommoir||William Shakespeare, Hamlet|
|Émile Zola, Germinal||William Shakespeare, MacBeth|
|Victor Hugo, Les Misérables||Lewis Caroll, Alice in Wonderland|
|Marcel Proust, Du côté de chez Swann||Sir Arthur Conan Doyle, Sherlock Holmes|
|Stendhal, Le rouge et le noir||Herman Melville, Moby Dick ; or The Whale|
|Alexandre Dumas, Les trois mousquetaires||Mary Shelley, Frankenstein or The Modern Prometheus|
|Gustave Flaubert, Madame Bovary||Charles Dickens, Great Expectations|
The performance of correction reaches about 83%.
A more detailed analysis can be found in the project report.