Question

When I run this program, I get the error message:

??? Index exceeds matrix dimensions.
Error in ==> if a(1,i)==0

could you tell me why??

a = randi(5,4,100)-ones(4,100);

[n m]=size(a);

for i=1:m
    if a(1,i)==0
        a(:,i)=[];
    end
end

Answer 1

The reason is that you are removing columns from your matrix, so inside the for loop you are reducing its dimension. Then you try to access a column with an index which refers to the original matrix, before the columns were removed.

Try this instead:

a = randi(5,4,100)-1;
ind2remove = (a(1,:) == 0);
a(:,ind2remove) = [];