TF-IDF in NLP stands for Term Frequency – Inverse document frequency. It is a very popular topic in Natural Language Processing which generally deals with human languages. During any text processing, cleaning the text (preprocessing) is vital. Further, the cleaned data needs to be converted into a numerical format where each word is represented by a matrix (word vectors). This is also known as word embedding
Term Frequency (TF) = (Frequency of a term in the document)/(Total number of terms in documents)
Inverse Document Frequency(IDF) = log( (total number of documents)/(number of documents with term t))
TF.IDF = (TF).(IDF)
Bigrams: Bigram is 2 consecutive words in a sentence. E.g. “The boy is playing football”. The bigrams here are:
The boy Boy is Is playing Playing football
Trigrams: Trigram is 3 consecutive words in a sentence. For the above example trigrams will be:
The boy is Boy is playing Is playing football
From the above bigrams and trigram, some are relevant while others are discarded which do not contribute value for further processing.
Let us say from a document we want to find out the skills required to be a “Data Scientist”. Here, if we consider only unigrams, then the single word cannot convey the details properly. If we have a word like ‘Machine learning developer’, then the word extracted should be ‘Machine learning’ or ‘Machine learning developer’. The words simply ‘Machine’, ‘learning’ or ‘developer’ will not give the expected result.
Code – Illustrating the detailed explanation for trigrams
Features : ['10 experience working', '11 exposure implementing', 'able work minimal', 'accounts commerce added', 'analysis recognition face', 'analytics contextual image', 'analytics nlp ensemble', 'applying data science', 'bagging boosting text', 'beyond existing learn', 'boosting text analytics', 'building using logistics', 'building using supervised', 'classification facial expression', 'classifier deep learning', 'commerce added advantage', 'complex engineering analysis', 'contextual image processing', 'creative projects work', 'data science problem', 'data science solutions', 'decisions report progress', 'deep learning analytics', 'deep learning framework', 'deep learning neural', 'demonstrated development role', 'demonstrated leadership role', 'description machine learning', 'detection tracking classification', 'development role machine', 'direction project less', 'domains essential position', 'domains like healthcare', 'ensemble classifier deep', 'existing learn quickly', 'experience object detection', 'experience working multiple', 'experienced technical personnel', 'expertise visualizing manipulating', 'exposure implementing data', 'expression analysis recognition', 'extensively worked python', 'face iris finger', 'facial expression analysis', 'finance accounts commerce', 'forest bagging boosting', 'framework tensorflow keras', 'good oral written', 'guidance direction project', 'guidance make decisions', 'healthcare finance accounts', 'implementing data science', 'including provide guidance', 'innovative creative projects', 'iris finger gesture', 'job description machine', 'keras or pytorch', 'leadership role projects', 'learn quickly new', 'learning analytics contextual', 'learning framework tensorflow', 'learning neural networks', 'learning projects including', 'less experienced technical', 'like healthcare finance', 'linear regression svm', 'logistics regression linear', 'machine learning developer', 'machine learning projects', 'make decisions report', 'manipulating big datasets', 'minimal guidance make', 'model building using', 'motivated able work', 'multiple domains like', 'must self motivated', 'new domains essential', 'nlp ensemble classifier', 'object detection tracking', 'oral written communication', 'perform complex engineering', 'problem solving proven', 'problem statements bring', 'proficiency deep learning', 'proficiency problem solving', 'project less experienced', 'projects including provide', 'projects work spare', 'proven perform complex', 'proven record working', 'provide guidance direction', 'quickly new domains', 'random forest bagging', 'recognition face iris', 'record working innovative', 'regression linear regression', 'regression svm random', 'role machine learning', 'role projects including', 'science problem statements', 'science solutions production', 'self motivated able', 'solutions production environments', 'solving proven perform', 'spare time plus', 'statements bring insights', 'supervised unsupervised algorithms', 'svm random forest', 'tensorflow keras or', 'text analytics nlp', 'tracking classification facial', 'using logistics regression', 'using supervised unsupervised', 'visualizing manipulating big', 'work minimal guidance', 'work spare time', 'working innovative creative', 'working multiple domains'] X1 : [[0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0] ... [0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0]] Scores : [[0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.] ... [0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.]] Words head : term rank 41 extensively worked python 1.000000 79 oral written communication 0.707107 47 good oral written 0.707107 72 model building using 0.673502 27 description machine learning 0.577350 70 manipulating big datasets 0.577350 67 machine learning developer 0.577350
Now, if w do it for bigrams then the initial part of code will remain the same. Only the bigram formation part will change.
Code : Python code for implementing bigrams
X1 : [[0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0] ... [0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0] [0 0 0 ... 0 0 0]] Scores : [[0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.] ... [0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.] [0. 0. 0. ... 0. 0. 0.]] Words : term rank 50 great interpersonal 1.000000 110 skills abilities 1.000000 23 deep learning 0.904954 72 machine learning 0.723725 21 data science 0.723724 128 worked python 0.707107 42 extensively worked 0.707107
Likewise, we can obtain the TF IDF scores for bigrams and trigrams as per our use. These can help us get a better outcome without having to process more on data.
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