Zero out values ​​from a specific row in a matrix

I create a matrix, I need to reset all values ​​​​above or below a certain line

c = randi([50 90],1,900); % rows in the matrix before or after which you need to reset everything
x = rand(100,900);

I would appreciate any help

[Jan]

Does "reset" means, to set the value to 0? A small example with inputs and output would clarify this.

Answer 1

[DGM]

Depends if you want before or after. Since there's no specified mechanism to determine which, I'm assuming they're separate cases.

% a smaller array
sz = [10 10];
c = randi(round([0.5 0.9]*sz(1)),1,sz(2))

c = 1×10

5 5 8 8 7 6 5 7 7 7

x = rand(sz);

% above
xa = zeros(sz);
for col = 1:sz(2)
    xa(c(col):end,col) = x(c(col):end,col);
end
xa

xa = 10×10

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.6705 0.3275 0 0 0 0 0.8203 0 0 0 0.3977 0.2444 0 0 0 0.2563 0.6388 0 0 0 0.3504 0.4670 0 0 0.8608 0.6775 0.7311 0.6058 0.9829 0.5098 0.2348 0.4727 0.5051 0.7958 0.2300 0.5589 0.2007 0.7440 0.6406 0.1086 0.3023 0.2689 0.6540 0.5244 0.9616 0.0880 0.9428 0.1761 0.6237 0.5623 0.7242 0.2876 0.3713 0.6931 0.6045 0.1354 0.0207 0.3005 0.6675 0.9878

% below
xb = zeros(sz);
for col = 1:sz(2)
    xb(1:c(col),col) = x(1:c(col),col);
end
xb

xb = 10×10

0.2351 0.8935 0.6577 0.1085 0.7050 0.7653 0.5715 0.1200 0.3469 0.8277 0.8900 0.0832 0.3699 0.4257 0.3712 0.8449 0.8821 0.3460 0.0425 0.6749 0.7048 0.9170 0.8989 0.5342 0.1087 0.4904 0.3728 0.1454 0.6048 0.0438 0.9782 0.3588 0.9342 0.3823 0.5303 0.7890 0.3342 0.0637 0.2030 0.5178 0.6705 0.3275 0.4531 0.0285 0.0355 0.8376 0.8203 0.1705 0.6936 0.4366 0 0 0.6351 0.0355 0.8810 0.2563 0 0.7491 0.8071 0.5694 0 0 0.1182 0.9483 0.8608 0 0 0.6058 0.9829 0.5098 0 0 0.5051 0.7958 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0