python - 如何从多个列表中找到最大值？

Question

我有多个相同大小的列表(或 numpy 数组)，我想返回一个相同大小的数组，每个点都有最大值。

例如，

A = [[0,1,0,0,3,0],[1,0,0,2,0,3]]
B = [[1,0,0,0,0,4],[0,5,6,0,1,1]]
C = numpy.zeros_like(A)
for i in xrange(len(A)):
    for j in xrange(len(A[0])):
        C[i][j] = max(A[i][j],B[i][j])

结果是 C = [[1,1,0,0,3,4],[1,5,6,2,1,3]]

这工作正常，但效率不高 - 特别是对于我拥有的数组大小和我需要比较的数组数量。我怎样才能更有效地做到这一点？

Answer 1

使用numpy.maximum :

numpy.maximum(x1, x2[, out])
Element-wise maximum of array elements.

Compare two arrays and returns a new array containing the element-wise maxima. If one of the elements being compared is a nan, then that element is returned. If both elements are nans then the first is returned. The latter distinction is important for complex nans, which are defined as at least one of the real or imaginary parts being a nan. The net effect is that nans are propagated.