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NLP Fundamentals — Text Processing, Embeddings and Classification

Core MLNLP🟢 Free Lesson

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Specialized Topics

Natural Language Processing — Teaching Computers to Read

NLP enables computers to understand, interpret, and generate human language — bridging the gap between raw text and actionable insights.

  • Text Preprocessing — tokenization, stemming, and lemmatization clean and normalize raw text
  • TF-IDF and Bag of Words — simple but effective vectorization methods for text classification
  • Word Embeddings — Word2Vec and GloVe capture semantic relationships between words in dense vector space

"Language is the house of being." — Martin Heidegger

NLP Fundamentals — Complete Guide

Natural Language Processing enables computers to understand and generate human language.


Mathematical Foundations

TF-IDF Formula

where:

(term frequency)

(inverse document frequency)

Cosine Similarity (for embeddings)

Word2Vec Skip-gram Objective


NLP Preprocessing Pipeline

NLP Text Preprocessing PipelineRaw Text"I LOVE ML!!!"TokenizeSplit → words["I","LOVE","ML"]Lowercase→ lowercase["i","love","ml"]StopwordsRemove "i"["love","ml"]Stem/Lemma→ root form["love","ml"]Vector→ numbersTokenization ComparisonWord Tokenization"Don't" → ["Do", "n't"]"New-York" → ["New", "York"]Simple, fast, loses contextSubword (BPE)"unhappiness" → ["un","happi","ness"]Handles rare wordsUsed by BERT, GPTCharacter Tokenization"Hello" → ["H","e","l","l","o"]No OOV issuesLong sequences, slow

Bag of Words and TF-IDF

Word Embeddings Space

Word Embeddings — Semantic Vector SpaceOne-Hot Encoding (Sparse)king = [1, 0, 0, 0, 0]queen = [0, 1, 0, 0, 0]man = [0, 0, 1, 0, 0]woman = [0, 0, 0, 1, 0]cat = [0, 0, 0, 0, 1]• All orthogonal (dot = 0)• No semantic meaning• Sparse, high-dimensionalWord Embedding (Dense)kingqueenmanwomancatking - man + woman ≈ queenSemantic relationships preserved!Dense, low-dimensional, meaningful

Word Embeddings


N-grams and Local Word Order

N-grams: Capturing Word OrderUnigrams (n=1)"I love ML" →["I", "love", "ML"]• No word order• Bag of Words approach• Fast, simple• "not good" = "good" (problem!)Bigrams (n=2)"I love ML" →["I love", "love ML"]• Captures adjacent pairs• "not good" captured• Vocabulary grows• Better than unigramsTrigrams (n=3)"I love ML" →["I love ML"]• Full phrase context• Very large vocabulary• Sparse features• Usually n=1 or 2 is best

Text Classification


Key Takeaways


What to Learn Next

-> Transformers Learn the self-attention architecture that revolutionized NLP and powers modern AI.

-> BERT Master encoder-only transformers for text classification, NER, and question answering.

-> GPT Architecture Understand decoder-only transformers that power autoregressive text generation.

-> Naive Bayes Learn the simple probabilistic classifier often used as a strong NLP baseline.

-> RNN and LSTM Explore sequential models that were the dominant NLP approach before transformers.

-> GANs Discover generative adversarial networks for text generation and style transfer.

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