MATLAB索引问题 [英] MATLAB indexing question

问题描述

我有一个矩阵，例如

A = [ 1 2 3; 4 5 6; 7 8 9] ;

和一个大小为1x3的向量，它指定每行中哪个元素是我要查找的元素 - 即如果

and a vector of size 1x3 which specifies which element in each row is the one I'm looking for - i.e. If

vector = [ 1 2 1 ]

然后所需的输出是

[ 1 5 7 ]

因为 1 是1中的第1个元素'st row， 5 是第2行中的2'，而 7 是第1行第3行中的元素。

since 1 is the 1'st element in the 1'st row, 5 is the 2'nd in the 2'nd row, and 7 is the 1'st element in the 3'rd row.

我如何实现这一目标？无法找到内置函数来做到这一点，这让我感到惊讶。

How do I achieve this? Couldn't find a built in function to do this, which surprised me.

推荐答案

首先，Matlab中的索引去了从上到下。

所以在你的情况下 A [1] = 1，A [2] = 4，A [3] = 7

First of all, the indexes in Matlab go from top to bottom.
So in your case A[1] = 1 , A[2] = 4 , A[3] = 7

也就是说，在A'上工作会更容易，因为它有点琐碎。

That said, it would be easier to work on A' , because its a bit more trivial.

B = A';

B((vector + [0:2].* 3))

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