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，它指定每行中的哪个元素是我正在寻找的元素 - 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 ]

那么所需的输出是

[ 1 5 7 ]

因为 1 是第一行的第一元素，5 是第二行的第二元素，7 是第 3 行中的第 1 个元素.

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?找不到可以执行此操作的内置函数，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中的索引是自上而下的.
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，因为它更微不足道.

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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