October 2021
Intermediate to advanced
289 pages
8h 31m
Chinese
Content preview from 数据科学中的实用统计学(第2版)
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250
｜
第
7
章
df = sp500_px.loc[sp500_px.index >= '2011-01-01', syms1].transpose()
Z = linkage(df, method='complete')
7.3.2
树状图
层次聚类非常适合通过图形化方式表示成一棵树，这种表示称为
树状图
（
dendrogram
）， 这
个名称来自于希腊语
dendro
（树）和
gramma
（图画）
。在
R
中，使用
plot
命令生成树状
图非常容易：
plot(hcl)
在
Python
中，可以使用
dendrogram
方法绘制出
linkage
函数的结果：
fig, ax = plt.subplots(figsize=(5, 5))
dendrogram(Z, labels=df.index, ax=ax, color_threshold=0)
plt.xticks(rotation=90)
ax.set_ylabel('distance')
结果如图
7-8
所示（请注意，我们绘制出的是彼此相似的公司，不是日期）。树的叶子表示
记录，树的分支的长度表示簇之间的相异度。
Google
和
Amazon
的收益之间的差异很大
，
它们与其他股票之间的差异更大。石油股票（
SLB
、
CVX
、
XOM
、
COP
）
聚集成了一个
簇，
Apple
（
AAPL
）自成一簇，其他股票彼此之间非常相似。
图 7-8：股票的树状图
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