scipy.spatial.distance.squareform的反函数

Question

scipy.spatial.distance.squareform有反函数吗？如果没有，那么处理大型距离矩阵的最佳方法是什么？

- bougui

Answer 1

根据文档，squareform 是其自身的反函数： http://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.distance.squareform.html

- Sideshow Bob

Answer 2

实际上，这个lambda表达式非常高效：

In [1]: unsquareform = lambda a: a[numpy.nonzero(numpy.triu(a))]

例如：

In [2]: scipy.spatial.distance.pdist(numpy.arange(12).reshape((4,3)))
Out[2]:
array([  5.19615242,  10.39230485,  15.58845727,   5.19615242,
        10.39230485,   5.19615242])

并且

In [3]: unsquareform(scipy.spatial.distance.squareform(scipy.spatial.distance.pdist(numpy.arange(12).reshape((4,3)))))
Out[3]:
array([  5.19615242,  10.39230485,  15.58845727,   5.19615242,
        10.39230485,   5.19615242])

- bougui