如何在Matlab中从矩阵中提取非垂直列 [英] How to extract non-vertical column from matrix in Matlab

问题描述

我有一个矩阵A和一个向量b，它为矩阵的每个对应行指定要提取的元素的列索引.

I have matrix A and a vector b, which specifies column index of the element to be extracted for each corresponding row of the matrix.

例如

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

b = [1 3 2]'

我想在输出上显示c = [1 6 8]'.如何实现呢?

I'd like to have c = [1 6 8]' on output. How to achieve this?

我尝试了A(:, b)，但是它并不能按我的需要工作.

I tried A(:, b), but it doesn't work as I need.

推荐答案

作为@dantswain解决方案的替代方法，假设您始终从列中进行选择，则可以直接转到线性索引:

As an alternative to @dantswain's solution, you can go to the linear indices directly, assuming you're always selecting from the columns:

r = size(A,1);
A( (1:r).' + (b-1) * r)

这会更快，但不一定更清楚.

This will be faster, but not necessarily clearer.

不幸的是，没有一个优雅的解决方案.

Unfortunately, there isn't an elegant solution.

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