Quanti cluster di cereali?

Nel video hai visto come scegliere un buon numero di cluster per un insieme di dati usando il grafico dell'inerzia di k-means. Ti viene fornito un array samples che contiene le misure (come area, perimetro, lunghezza e altre) di campioni di cereali. Qual è un buon numero di cluster in questo caso?

KMeans e PyPlot (plt) sono già stati importati per te.

Questo insieme di dati proviene dall'UCI Machine Learning Repository.

Questo esercizio fa parte del corso

Apprendimento non supervisionato in Python

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Istruzioni dell'esercizio

Per ognuno dei valori di k forniti, esegui i seguenti passaggi:
Crea un'istanza KMeans chiamata model con k cluster.
Adatta il modello ai dati dei cereali samples.
Aggiungi il valore dell'attributo inertia_ di model alla lista inertias.
Il codice per tracciare ks rispetto a inertias è già pronto: premi Invia per vedere il grafico!

Esercizio pratico interattivo

Prova a risolvere questo esercizio completando il codice di esempio.

ks = range(1, 6)
inertias = []

for k in ks:
    # Create a KMeans instance with k clusters: model
    ____
    
    # Fit model to samples
    ____
    
    # Append the inertia to the list of inertias
    ____
    
# Plot ks vs inertias
plt.plot(ks, inertias, '-o')
plt.xlabel('number of clusters, k')
plt.ylabel('inertia')
plt.xticks(ks)
plt.show()

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Questo esercizio fa parte del corso

Apprendimento non supervisionato in Python

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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: Quanti cluster?Exercise 3: Clustering di punti 2D Exercise 4: Esamina il tuo clustering Exercise 5: Valutare un clustering Exercise 6: Quanti cluster di cereali?

Esercizio in corso

Exercise 7: Valutare il clustering dei cereali Exercise 8: Trasformare le caratteristiche per cluster più efficaci Exercise 9: Scalare i dati sui pesci per il clustering Exercise 10: Clustering dei dati sui pesci Exercise 11: Clustering dei titoli azionari con KMeans Exercise 12: Quali titoli si muovono insieme?

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: Visualizing the PCA transformation Exercise 2: Correlated data in nature Exercise 3: Decorrelating the grain measurements with PCA Exercise 4: Principal components Exercise 5: Intrinsic dimension Exercise 6: The first principal component Exercise 7: Variance of the PCA features Exercise 8: Intrinsic dimension of the fish data Exercise 9: Dimension reduction with PCA Exercise 10: Dimension reduction of the fish measurements Exercise 11: A tf-idf word-frequency array Exercise 12: Clustering Wikipedia part I Exercise 13: Clustering Wikipedia part 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