如何很好地处理[:-0]切片? [英] How to nicely handle [:-0] slicing?

问题描述

在实现自相关函数时，我有一个类似

In implementing an autocorrelation function I have a term like

for k in range(start,N):
    c[k] = np.sum(f[:-k] * f[k:])/(N-k)

现在，如果start = 1，一切都可以正常工作，但是我想很好地处理0情况下的开始，而没有条件.

Now everything works fine if start = 1 but I'd like to handle nicely the start at 0 case without a conditional.

很明显，它是不起作用的，因为f[:-0] == f[:0]并返回一个空数组，而在这种情况下，我需要完整的数组.

Obviously it doesn't work as it is because f[:-0] == f[:0] and returns an empty array, while I'd want the full array in that case.

推荐答案

在这种情况下请勿使用负索引

Don't use negative indices in this case

f[:len(f)-k]

对于k == 0，它返回整个数组.对于任何其他正数k，它等效于f[:-k]

For k == 0 it returns the whole array. For any other positive k it's equivalent to f[:-k]

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