How do I fill in a matrix in this way?

I want to fill in a large matrix and know what certain rows/columns/areas are. For example, say I have a 900x900 matrix. The 300th row may be 400, and the space from the 3rd row to the 9th row in the 4th to 9th columns is 800. The rest could be 200. How do I create a matrix by knowing these things?

Answer 1

[Image Analyst]

Try this with your matrix, m

m = 200 * ones(200); % First initialize to all 200
m(300, :) = 400;  % Set row 300, all columns, to 400.
m(3:9, 4:9) = 800;  % Set this block to be all 800

[Nick Thomas]

Thank you! That helps a lot.