I have a 300 x 150 zeros matrix and want to change only the lower triangular elements to 1, How do I do that?

Everything is in the title really, I need to change the lower triangular elements of this zeros matrix to 1, how can I do this easily?

[Stephen23]

https://www.mathworks.com/help/matlab/ref/tril.html

Answer 1

[Image Analyst]

You don't even need your original zeros matrix (let's say you called your original matrix "z") since it gets completely overwritten by 0's and 1's.

Simply make a 300 x 150 matrix of zeros with the lower left triangle of 1's like this:

z = [zeros(150); tril(ones(150), 0)];
% Now verify and display it.
size(z)

ans = 1×2

300 150

imshow(z)
axis('on', 'image')

Answer 2

[KSSV]

idx = ones(300,150) ;
idx = tril(idx,1) ; % Make 1's at lower triangular part 
A = rand(300,150) ;  % given matrix 
A(idx==1) = 1 ;     % replace lower triangular part with 1

Answer 3

[Jan]

In Matlb >= R2016b:

M = (1:300).' >= (1:150);

For older Matlab versions:

M = bsxfun(@ge, (1:300).', 1:150);

Answer 4

[Abdurayimov Orzumurod]

idx = bir (300,150);

idx = tril(idx,1) ; % Pastki uchburchak qismiga 1 qo'ying

A = rand (300,150); % berilgan matritsa

A(idx==1) = 1 ; % pastki uchburchak qismini 1 bilan almashtiring