更新矩阵，每行单列，其中行索引在 vecor 中 [英] Update matrix, single column per row where row index is in vecor

问题描述

有没有办法更新矩阵每一行中的不同列，其中行索引存储在向量中.

Is there a way to update different column in each row of matrix, where row indices are stored in vector.

示例

mx = zeros(10,10);
cols = [2 3 5 4 6 8 9 1 2 3]';
for i = 1:size(mx,1)
    mx(i,cols(i)) = 1;
end
mx

生产

0   1   0   0   0   0   0   0   0   0
0   0   1   0   0   0   0   0   0   0
0   0   0   0   1   0   0   0   0   0
0   0   0   1   0   0   0   0   0   0
0   0   0   0   0   1   0   0   0   0
0   0   0   0   0   0   0   1   0   0
0   0   0   0   0   0   0   0   1   0
1   0   0   0   0   0   0   0   0   0
0   1   0   0   0   0   0   0   0   0
0   0   1   0   0   0   0   0   0   0

问题是，我能不能不用 for 循环?

The question is, whether I can do it without the for loop?

推荐答案

您可以使用单个数字对矩阵中的元素进行寻址.在这种情况下，元素按列编号(1-10 是第一列，11-20 是第二列......)并且有一个函数 sub2ind 可以为您计算元素编号.在您的情况下，它非常简单，因为它是 10x10，因此您可以手动完成，但我仍然会推荐该功能.

You can address elements in a matrix with a single number. In this case the elements are numbered columnwise (1-10 is the first column, 11-20 the secound...) and there is a function sub2ind to calculate the element number for you. In your case its pretty easy, because its a 10x10 so you could do it manually, but i would still recommend the function.

mx = zeros(10,10);
rows = 1:size(mx,1); %create the row indices 
cols = [2 3 5 4 6 8 9 1 2 3];
X=sub2ind(size(mx),rows,cols)
mx(X)=1;
mx

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