Logical indexing is one way. Both Doug and Loren have a mini tutorial on it. To get say all elements of X(1,:), that are say 0-50, replace the ':' with a logical argument. e.g. A = X(1, X(1,:) > 50 ); B = X(1, X(1,:) < 51); for both rows A = X(:, X(1,:) > 50); B = X(:, X(1,:) < 51);
The 'X(1,:) > 50' bit is looking up all elements in the first row of X that is GT 50, and then using that to create the new array.
As you can guess it is possible to use multiple logical arguments with '&&' etc.