Python集群“纯度”指标
Python集群“纯度”指标
提问于 2015-12-03 00:14:17
我正在使用来自sklearn.mixture的Gaussian Mixture Model (GMM)来执行我的数据集的聚类。
我可以使用函数score()来计算模型下的对数概率。
但是，我正在寻找在this article中定义的名为“purity”的指标。
我如何在Python中实现它？我当前的实现如下所示：
from sklearn.mixture import GMM
# X is a 1000 x 2 array (1000 samples of 2 coordinates).
# It is actually a 2 dimensional PCA projection of data
# extracted from the MNIST dataset, but this random array
# is equivalent as far as the code is concerned.
X = np.random.rand(1000, 2)
clusterer = GMM(3, 'diag')
clusterer.fit(X)
cluster_labels = clusterer.predict(X)
# Now I can count the labels for each cluster..
count0 = list(cluster_labels).count(0)
count1 = list(cluster_labels).count(1)
count2 = list(cluster_labels).count(2)但是我不能遍历每个集群来计算混淆矩阵(根据这个question)
回答 1
Stack Overflow用户
发布于 2017-07-06 08:21:37
一份很晚的贡献。
您可以尝试像这样实现它，就像在这个gist中一样
def purity_score(y_true, y_pred):
"""Purity score
Args:
y_true(np.ndarray): n*1 matrix Ground truth labels
y_pred(np.ndarray): n*1 matrix Predicted clusters
Returns:
float: Purity score
"""
# matrix which will hold the majority-voted labels
y_voted_labels = np.zeros(y_true.shape)
# Ordering labels
## Labels might be missing e.g with set like 0,2 where 1 is missing
## First find the unique labels, then map the labels to an ordered set
## 0,2 should become 0,1
labels = np.unique(y_true)
ordered_labels = np.arange(labels.shape[0])
for k in range(labels.shape[0]):
y_true[y_true==labels[k]] = ordered_labels[k]
# Update unique labels
labels = np.unique(y_true)
# We set the number of bins to be n_classes+2 so that
# we count the actual occurence of classes between two consecutive bins
# the bigger being excluded [bin_i, bin_i+1[
bins = np.concatenate((labels, [np.max(labels)+1]), axis=0)
for cluster in np.unique(y_pred):
hist, _ = np.histogram(y_true[y_pred==cluster], bins=bins)
# Find the most present label in the cluster
winner = np.argmax(hist)
y_voted_labels[y_pred==cluster] = winner
return accuracy_score(y_true, y_voted_labels)页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/34047540
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