在 numpy/scipy 中查找函数 matlab [英] find function matlab in numpy/scipy

问题描述

对于 numpy/scipy，matlab 中是否有 find(A>9,1) 的等效函数.我知道 numpy 中有 nonzero 函数，但我需要的是第一个索引，以便我可以在另一个提取的列中使用第一个索引.

Is there an equivalent function of find(A>9,1) from matlab for numpy/scipy. I know that there is the nonzero function in numpy but what I need is the first index so that I can use the first index in another extracted column.

例如:A = [ 1 2 3 9 6 4 3 10 ]find(A>9,1) 将在 matlab 中返回索引 4

Ex: A = [ 1 2 3 9 6 4 3 10 ] find(A>9,1) would return index 4 in matlab

推荐答案

numpy中find的等价物是nonzero，但是不支持第二个参数.但是你可以做这样的事情来获得你正在寻找的行为.

The equivalent of find in numpy is nonzero, but it does not support a second parameter. But you can do something like this to get the behavior you are looking for.

B = nonzero(A >= 9)[0] 

但是，如果您正在寻找的只是找到满足条件的第一个元素，那么您最好使用 max.

But if all you are looking for is finding the first element that satisfies a condition, you are better off using max.

例如，在 matlab 中，find(A >= 9, 1) 将等同于 [~, idx] = max(A >= 9).numpy 中的等效函数如下.

For example, in matlab, find(A >= 9, 1) would be the same as [~, idx] = max(A >= 9). The equivalent function in numpy would be the following.

idx = (A >= 9).argmax()

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