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

Question

Alexandra Huff 2016-8-7

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/298731-how-do-i-fix-my-code-to-produce-ones-along-the-reverse-diagonal

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
显示无隐藏无

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 2016-11-15

编辑：Nava Subedi 2016-11-15

在 MATLAB Online 中打开

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.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Star Strider 2016-8-7

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/298731-how-do-i-fix-my-code-to-produce-ones-along-the-reverse-diagonal#answer_231035

编辑：Star Strider 2016-8-7

在 MATLAB Online 中打开

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.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

HASTI HARISH 2018-6-19

how can we do the same without a for loop

请先登录，再进行评论。

Answer 2

James Tursa 2016-11-15

3
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/298731-how-do-i-fix-my-code-to-produce-ones-along-the-reverse-diagonal#answer_243434

在 MATLAB Online 中打开

Yet another way using linear indexing:

I = zeros(n);
I(n:n-1:end-1) = 1;

6 个评论
显示 4更早的评论隐藏 4更早的评论

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 2020-6-12

在 MATLAB Online 中打开

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;

请先登录，再进行评论。

Answer 3

Image Analyst 2016-8-7

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/298731-how-do-i-fix-my-code-to-produce-ones-along-the-reverse-diagonal#answer_231034

在 MATLAB Online 中打开

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