两个数组定义二维坐标，如数组索引，在MATLAB /八度 [英] two arrays defining 2d coordinates, as array indices, in matlab/octave

问题描述

我有一个二维数组，称之为A。我有两个其他二维数组，称他们为九和IY。我想创建一个输出数组，其元素是A在由x_idx和y_idx提供的指数对的元素。我可以用一个循环做到这一点如下：

I have a 2D array, call it 'A'. I have two other 2D arrays, call them 'ix' and 'iy'. I would like to create an output array whose elements are the elements of A at the index pairs provided by x_idx and y_idx. I can do this with a loop as follows:

for i=1:nx
    for j=1:ny
        output(i,j) = A(ix(i,j),iy(i,j));
    end
end

我怎么能做到这一点不循环？如果我做输出= A（IX，IY），我得到一个值的整个范围内（九）X（IY）。

How can I do this without the loop? If I do output = A(ix,iy), I get the value of A over the whole range of (ix)X(iy).

感谢您，
杰森

Thank you, Jason

推荐答案

一个更快的方法是使用线性索引直接，而无需调用SUB2IND：

A faster way is to use linear indexing directly without calling SUB2IND:

output = A( size(A,1)*(iy-1) + ix )

...想矩阵A为一维数组（列方式排列）

... think of the matrix A as a 1D array (column-wise order)

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