Um array de frequência de palavras com tf-idf

Neste exercício, você vai criar um array de frequência de palavras com tf-idf para uma coleção simples de documentos. Para isso, use o TfidfVectorizer do sklearn. Ele transforma uma lista de documentos em um array de frequência de palavras, que é retornado como uma csr_matrix. Ele tem os métodos fit() e transform() como outros objetos do sklearn.

Você recebe uma lista documents de documentos simples sobre animais de estimação.

Este exercício faz parte do curso

Unsupervised Learning em Python

Instruções do exercício

Importe TfidfVectorizer de sklearn.feature_extraction.text.
Crie uma instância de TfidfVectorizer chamada tfidf.
Aplique o método .fit_transform() de tfidf a documents e atribua o resultado a csr_mat. Este é um array de frequência de palavras no formato csr_matrix.
Inspecione csr_mat chamando seu método .toarray() e imprimindo o resultado. Isso já foi feito para você.
As colunas do array correspondem a palavras. Obtenha a lista de palavras chamando o método .get_feature_names_out() de tfidf e atribua o resultado a words.

Exercício interativo prático

Experimente este exercício completando este código de exemplo.

# Import TfidfVectorizer
from ____ import ____

# Create a TfidfVectorizer: tfidf
tfidf = ____ 

# Apply fit_transform to document: csr_mat
csr_mat = ____

# Print result of toarray() method
print(csr_mat.toarray())

# Get the words: words
words = ____

# Print words
print(words)

Editar e executar o código

Este exercício faz parte do curso

Unsupervised Learning em Python

IntermediárioNível de habilidade

4.8+

Iniciar curso de graça

Learn how to discover the underlying groups (or "clusters") in a dataset. By the end of this chapter, you'll be clustering companies using their stock market prices, and distinguishing different species by clustering their measurements.

Exercise 1: Unsupervised Learning Exercise 2: How many clusters?Exercise 3: Clustering 2D points Exercise 4: Inspect your clustering Exercise 5: Evaluating a clustering Exercise 6: How many clusters of grain?Exercise 7: Evaluating the grain clustering Exercise 8: Transforming features for better clusterings Exercise 9: Scaling fish data for clustering Exercise 10: Clustering the fish data Exercise 11: Clustering stocks using KMeans Exercise 12: Which stocks move together?

In this chapter, you'll learn about two unsupervised learning techniques for data visualization, hierarchical clustering and t-SNE. Hierarchical clustering merges the data samples into ever-coarser clusters, yielding a tree visualization of the resulting cluster hierarchy. t-SNE maps the data samples into 2d space so that the proximity of the samples to one another can be visualized.

Exercise 1: Visualizing hierarchies Exercise 2: How many merges?Exercise 3: Hierarchical clustering of the grain data Exercise 4: Hierarchies of stocks Exercise 5: Cluster labels in hierarchical clustering Exercise 6: Which clusters are closest?Exercise 7: Different linkage, different hierarchical clustering!Exercise 8: Intermediate clusterings Exercise 9: Extracting the cluster labels Exercise 10: t-SNE for 2-dimensional maps Exercise 11: t-SNE visualization of grain dataset Exercise 12: A t-SNE map of the stock market

Dimension reduction summarizes a dataset using its common occuring patterns. In this chapter, you'll learn about the most fundamental of dimension reduction techniques, "Principal Component Analysis" ("PCA"). PCA is often used before supervised learning to improve model performance and generalization. It can also be useful for unsupervised learning. For example, you'll employ a variant of PCA will allow you to cluster Wikipedia articles by their content!

Exercise 1: Visualizando a transformação PCA Exercise 2: Dados correlacionados na natureza Exercise 3: Decorrelacionando as medições de grãos com PCA Exercise 4: Componentes principais Exercise 5: Dimensão intrínseca Exercise 6: O primeiro componente principal Exercise 7: Variação dos recursos do site PCA Exercise 8: Dimensão intrínseca dos dados do peixe Exercise 9: Redução da dimensão com PCA Exercise 10: Redução da dimensão das medições de peixes Exercise 11: Um array de frequência de palavras com tf-idf

Exercício atual

Exercise 12: Agrupamento da Wikipédia parte I Exercise 13: Agrupamento de partes da Wikipédia II

In this chapter, you'll learn about a dimension reduction technique called "Non-negative matrix factorization" ("NMF") that expresses samples as combinations of interpretable parts. For example, it expresses documents as combinations of topics, and images in terms of commonly occurring visual patterns. You'll also learn to use NMF to build recommender systems that can find you similar articles to read, or musical artists that match your listening history!

Exercise 1: Non-negative matrix factorization (NMF)Exercise 2: Non-negative data Exercise 3: NMF applied to Wikipedia articles Exercise 4: NMF features of the Wikipedia articles Exercise 5: NMF reconstructs samples Exercise 6: NMF learns interpretable parts Exercise 7: NMF learns topics of documents Exercise 8: Explore the LED digits dataset Exercise 9: NMF learns the parts of images Exercise 10: PCA doesn't learn parts Exercise 11: Building recommender systems using NMF Exercise 12: Which articles are similar to 'Cristiano Ronaldo'?Exercise 13: Recommend musical artists part I Exercise 14: Recommend musical artists part II Exercise 15: Final thoughts