How do I fix my code to produce ones along the reverse diagonal?

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Alexandra Huff
Alexandra Huff 2016-8-7
评论： Bruno Luong 2020-6-12
Hi, I am having a problem with my code.
function I = reverse_diag(n)
I = zeros(n);
I(1: n+1 : n^2)=1;
I want my code to produce the ones on the reverse diagonal (top right to bottom left). I tried using fliplr because I believe, as of now, this is just a diagonal of ones from top left to bottom right. However, that is not working. Any suggestions?
  2 个评论
Image Analyst
Image Analyst 2016-8-7
编辑：Image Analyst 2016-8-7
Alexandra, you might like to read this link on formatting and this link so you can post better questions. You put code as text, and text as code format. I'll fix it this time for you. Also, you might give more descriptive subject lines - all your posts are like "how do I fix my code?" even though they're on different topic.
Don't forget to look at my answer below.
Nava Subedi
Nava Subedi 2016-11-15
编辑：Nava Subedi 2016-11-15
function s = reverse_diag(n)
I = zeros(n);
I(1: n+1 : n^2)=1;
s = flip(I, 2) % this line will reverse the elements in each row.

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采纳的回答

Star Strider
Star Strider 2016-8-7
编辑：Star Strider 2016-8-7
Assuming you can’t use the eye function, this works:
n = 5;
I = zeros(n);
for k1 = 1:n
I(k1, end-k1+1) = 1;
end
I =
0 0 0 0 1
0 0 0 1 0
0 0 1 0 0
0 1 0 0 0
1 0 0 0 0
EDIT — Added output matrix.

更多回答（3 个）

James Tursa
James Tursa 2016-11-15
Yet another way using linear indexing:
I = zeros(n);
I(n:n-1:end-1) = 1;
  6 个评论
显示 4更早的评论
Harshith Dhananjaya
Harshith Dhananjaya 2020-6-9
I tried this piece of code:
I = zeros(n);
I(n:n-1:end-1) = 1;
The result when n=1 provides answer [0] instead of [1]. All the other size matrices works fine.
Bruno Luong
Bruno Luong 2020-6-12
Correct, this is a bug for n==1. One can make it works for any n>=1 (but still not for n==0) with
I([1,n:n-1:1-1]) = 1;

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Image Analyst
Image Analyst 2016-8-7
Try this:
n = 5; % Whatever...
I = fliplr(eye(n))
I =
0 0 0 0 1
0 0 0 1 0
0 0 1 0 0
0 1 0 0 0
1 0 0 0 0
mouellou
mouellou 2018-12-21
Hi,
I'm a little late but I'm taking this class on coursera and here's my answer:
function I = reverse_diag(n)
I = zeros(n);
I(end-(n-1):-(n-1) : n)=1;
end
Hope it'll help someone

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