Assignment and accessing using indices

9 次查看（过去 30 天）
Jeff Wood
Jeff Wood 2016-6-5
评论： Jeff Wood 2016-6-6
I had a question about how to do a particular type of assignment using indices. The code below is a simplified example.
k = zeros(4,4);
v = [2,3];
k(v,v) = 1;
My intention was to get a result that looks like
ans =
[0, 0, 0, 0;
0, 1, 0, 0;
0, 0, 1, 0;
0, 0, 0, 0]
But unfortunately the result is:
ans =
[0, 0, 0, 0;
0, 1, 1, 0;
0, 1, 1, 0;
0, 0, 0, 0]
So my question is: Is there a way to access individual elements (rather than rectangular regions) without using a for loop (Which I understand is computationally expensive in MatLab)?

请先登录，再回答此问题。

采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2016-6-5
k = zeros(4,4);
v = [2,3];
idx=sub2ind(size(k),v,v)
k(idx) = 1;
  1 个评论
Jeff Wood
Jeff Wood 2016-6-6
Thanks,
I should have mentioned that v might be different for rows and columns (i.e. I was using the generic case where they were the same).

请先登录，再进行评论。

更多回答（2 个）

John BG
John BG 2016-6-6
diag([0 1 1 0])
John
jgb2012@sky.com
Chad Greene
Chad Greene 2016-6-5
Try this:
A = zeros(4);
lin = sub2ind([4 4],2:3,2:3);
A(lin) = 1;

类别

在 Help Center 和 File Exchange 中查找有关 Logical 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by