numpy cumsum函数的逆是什么? [英] What is the inverse of the numpy cumsum function?

问题描述

如果我有z = cumsum( [ 0, 1, 2, 6, 9 ] )，这给了我z = [ 0, 1, 3, 9, 18 ]，如何返回原始数组[ 0, 1, 2, 6, 9 ]?

If I have z = cumsum( [ 0, 1, 2, 6, 9 ] ), which gives me z = [ 0, 1, 3, 9, 18 ], how can I get back to the original array [ 0, 1, 2, 6, 9 ] ?

推荐答案

z[1:] -= z[:-1].copy()

又简短又甜美，没有缓慢的Python循环.我们对除第一个元素(z[1:])以外的所有元素和除最后一个元素(z[:-1])以外的所有元素进行查看，并逐元素相减.该副本可确保我们减去原始元素值，而不是我们正在计算的值. (在NumPy 1.13及更高版本上，则可以跳过copy调用.)

Short and sweet, with no slow Python loops. We take views of all but the first element (z[1:]) and all but the last (z[:-1]), and subtract elementwise. The copy makes sure we subtract the original element values instead of the values we're computing. (On NumPy 1.13 and up, you can skip the copy call.)

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