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"""
================================================================
Biclustering documents with the Spectral Co-clustering algorithm
================================================================
This example demonstrates the Spectral Co-clustering algorithm on the
twenty newsgroups dataset. The 'comp.os.ms-windows.misc' category is
excluded because it contains many posts containing nothing but data.
The TF-IDF vectorized posts form a word frequency matrix, which is
then biclustered using Dhillon's Spectral Co-Clustering algorithm. The
resulting document-word biclusters indicate subsets words used more
often in those subsets documents.
For a few of the best biclusters, its most common document categories
and its ten most important words get printed. The best biclusters are
determined by their normalized cut. The best words are determined by
comparing their sums inside and outside the bicluster.
For comparison, the documents are also clustered using
MiniBatchKMeans. The document clusters derived from the biclusters
achieve a better V-measure than clusters found by MiniBatchKMeans.
"""
import operator
from collections import defaultdict
from time import time
import numpy as np
from sklearn.cluster import MiniBatchKMeans, SpectralCoclustering
from sklearn.datasets import fetch_20newsgroups
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.metrics.cluster import v_measure_score
def number_normalizer(tokens):
"""Map all numeric tokens to a placeholder.
For many applications, tokens that begin with a number are not directly
useful, but the fact that such a token exists can be relevant. By applying
this form of dimensionality reduction, some methods may perform better.
"""
return ("#NUMBER" if token[0].isdigit() else token for token in tokens)
class NumberNormalizingVectorizer(TfidfVectorizer):
def build_tokenizer(self):
tokenize = super().build_tokenizer()
return lambda doc: list(number_normalizer(tokenize(doc)))
# exclude 'comp.os.ms-windows.misc'
categories = [
"alt.atheism",
"comp.graphics",
"comp.sys.ibm.pc.hardware",
"comp.sys.mac.hardware",
"comp.windows.x",
"misc.forsale",
"rec.autos",
"rec.motorcycles",
"rec.sport.baseball",
"rec.sport.hockey",
"sci.crypt",
"sci.electronics",
"sci.med",
"sci.space",
"soc.religion.christian",
"talk.politics.guns",
"talk.politics.mideast",
"talk.politics.misc",
"talk.religion.misc",
]
newsgroups = fetch_20newsgroups(categories=categories)
y_true = newsgroups.target
vectorizer = NumberNormalizingVectorizer(stop_words="english", min_df=5)
cocluster = SpectralCoclustering(
n_clusters=len(categories), svd_method="arpack", random_state=0
)
kmeans = MiniBatchKMeans(
n_clusters=len(categories), batch_size=20000, random_state=0, n_init=3
)
print("Vectorizing...")
X = vectorizer.fit_transform(newsgroups.data)
print("Coclustering...")
start_time = time()
cocluster.fit(X)
y_cocluster = cocluster.row_labels_
print(
"Done in {:.2f}s. V-measure: {:.4f}".format(
time() - start_time, v_measure_score(y_cocluster, y_true)
)
)
print("MiniBatchKMeans...")
start_time = time()
y_kmeans = kmeans.fit_predict(X)
print(
"Done in {:.2f}s. V-measure: {:.4f}".format(
time() - start_time, v_measure_score(y_kmeans, y_true)
)
)
feature_names = vectorizer.get_feature_names_out()
document_names = list(newsgroups.target_names[i] for i in newsgroups.target)
def bicluster_ncut(i):
rows, cols = cocluster.get_indices(i)
if not (np.any(rows) and np.any(cols)):
import sys
return sys.float_info.max
row_complement = np.nonzero(np.logical_not(cocluster.rows_[i]))[0]
col_complement = np.nonzero(np.logical_not(cocluster.columns_[i]))[0]
# Note: the following is identical to X[rows[:, np.newaxis],
# cols].sum() but much faster in scipy <= 0.16
weight = X[rows][:, cols].sum()
cut = X[row_complement][:, cols].sum() + X[rows][:, col_complement].sum()
return cut / weight
def most_common(d):
"""Items of a defaultdict(int) with the highest values.
Like Counter.most_common in Python >=2.7.
"""
return sorted(d.items(), key=operator.itemgetter(1), reverse=True)
bicluster_ncuts = list(bicluster_ncut(i) for i in range(len(newsgroups.target_names)))
best_idx = np.argsort(bicluster_ncuts)[:5]
print()
print("Best biclusters:")
print("----------------")
for idx, cluster in enumerate(best_idx):
n_rows, n_cols = cocluster.get_shape(cluster)
cluster_docs, cluster_words = cocluster.get_indices(cluster)
if not len(cluster_docs) or not len(cluster_words):
continue
# categories
counter = defaultdict(int)
for i in cluster_docs:
counter[document_names[i]] += 1
cat_string = ", ".join(
"{:.0f}% {}".format(float(c) / n_rows * 100, name)
for name, c in most_common(counter)[:3]
)
# words
out_of_cluster_docs = cocluster.row_labels_ != cluster
out_of_cluster_docs = np.where(out_of_cluster_docs)[0]
word_col = X[:, cluster_words]
word_scores = np.array(
word_col[cluster_docs, :].sum(axis=0)
- word_col[out_of_cluster_docs, :].sum(axis=0)
)
word_scores = word_scores.ravel()
important_words = list(
feature_names[cluster_words[i]] for i in word_scores.argsort()[:-11:-1]
)
print("bicluster {} : {} documents, {} words".format(idx, n_rows, n_cols))
print("categories : {}".format(cat_string))
print("words : {}\n".format(", ".join(important_words)))
|
