deleting some information in a matrix

Hi i'm quite a beginner on Matlab.

basically, the following is an example of a coding im working on, I'm trying to make B have the same number of dimensions as A using the following code. e.g

%c= is going to be a randomly generated number
A = zeros(100,100);
A(25:75,25:75) = 1;
B=I(:,1:100-C)

for simplicity sake, let's say c = 30 B will have 100x70 elements, and A will have 100x100, is there a way to

1. make B which is (100x70) have the same elements as A which is (100x100)., in other words, the elements that are not in the range are transformed into zeros?
2. another alternative i'm thinking of making is B= A(:,C:100+C)? but I would like the new elements (the elements i'm adding e.g(101 102 103...C) to become zeros. how would you go about that?

I'm looking for answers to both these questions,

Any help would be appreciated thank you

Answer 1

[Image Analyst]

You can extend B by a neat trick. Simply assign the (not yet existing) lower right element:

B(size(A, 1), size(A, 2)) = 0;  % Make B same size as A by appending zeros.

[hasan alhussaini]

perfect thank you!