Replacing elements in a matrix with the same row and column index

I am trying to create an alternative to the diagonal function. In doing so, i am creating a function using a user input for zeros. I want to replace the elements in that matrix that have the same row and column number with 1 instead of zeros. So element with the (row, column) location of say (1,1), (2,2), (3,3) and so on would be replaced with a 1 instead of a 0. Is there a way that i could do that.

This is my code so far,

function [matrix] = identity(s)

s= inputdlg('What is the scalar for matrix creation','Scalar value',[1, 40]);

data_s = str2num(s{:})

s_matrix= zeros(data_s)

Answer 1

[Walter Roberson]

s_matrix(1:s_data+1:end) = 1;

[Sanwal Yousaf]

Thanks a lot. Would you be kind enough to explain how this is working??

[Walter Roberson]

MATLAB linear indexing numbers down the columns. There are s_data entries in each column. If you consider index 1, the array at (1,1), linear 1+s_data correspond to the array at (1,2). The entry below that one, the second element of the diagonal, would then be at 1+s_data+1 which is a difference of s_data+1 from the original index. The entry to the right of that would be 1+s_data+1+s_data so the third element of the diagonal would be at 1+s_data+1+s_data+1 which is a difference of s_data+1 from the previous diagonal entry. We can then see that if we start at 1, and add s_data+1 each time, we follow the diagonal entries.