Insert smaller matrix into larger matrix with an equal number of columns.

Hey guys, I have two Matrices with the same number of columns but different number of rows, and I wish to insert Matrix A into Matrix B so in this example:

A = rand(25,50);
B = zeros(50,50);
[M N] = size(A); 

I then want to insert A into B, but I want to be able to define where I set them. So in this case:

X = 10;
Y = 35;

As they have the same number of columns I attempted to simply insert a couple of ways:

B(X:Y,1:end) = A; % This gives a "Subscripted assignment dimension mismatch"
B(X:Y, 1:N) = A; % Same error as above
B(X:Y,1:end) = A(1:M,1:end); % again same error

The output of this would be a (50,50) Matrix (B), with rows X:Y of B being replaced Matrix A.

Maybe a for loop would work here? I'm not entirely sure where to proceed from this point. Any help would be greatly appreciated.

Answer 1

[Jan]

X = 10;
Y = 35;

The problem is that X:Y has 26 elements, not 25. Remember: If A has 1 row only, you will not use: 10:11 but 10:10 only (which is the same as 10, of course).

Use X:Y-1 instead, then all 3 commands will work, or more general: X:X+M-1. I'd prefer the simpler:

B(X:(X + M - 1), :) = A;

[Donald Christie]

Well that simple error makes me feel like a right plum.

Cheers for the help.

[Jan]

@Donald: You can be sure, that I've recognized the error, because I'm used to do it by my own. I'm using the mentioned method to catch this mistake: "What are the indices for inserting 1 or 2 elements"?