MATLAB仅从矩阵中删除某些零

Question

I have seen plenty of answers regarding how to remove leading and/or trailing zeros, and how to remove all zeros from a vector or matrix. What I need to do, though, is only remove some of them. I have two matrices, and I only want to remove the entries where both of them are zero. They are two-dimensional x and y coordinates, solved using characteristics (I can give more detail if needed) and I just want to remove the values where both matrices contain zeros at the same indices. I can easily convert the matrices into vectors and work with vectors, so any help in either case would be greatly appreciated.

Answer 1

For the sake of simplicity, let's assume you're using vectors called X and Y (of the same length), and you want to remove only those entries where both vectors are zero. Here's how (not tested):

% Find the indexes where either X or Y is different from zero
% (these are the indexes of the components we want to keep)
I = find(X~=0 | Y~=0);

% Select the desired components from X and Y
X=X(I);
Y=Y(I);

Edit: As Oli has pointed out below (and stefano explained further), you should use logical indexing for better performance.