Brian - since A is an array, you will want to use the all function to ensure that all elements are positive and all elements are real. For example,
if ~all(isreal(A)) || ~all(A>0)
error('Amplitude must have only real and positive elements');
end
Try the above and see what happens!
With your code, with sum it seems like you want to check to see if the sum of all negative elements is not zero which may be okay, but should be discouraged when comparing singles or doubles to an integer (use a tolerance instead). And your second condition is trying to compare all elements of A against an array of ones and zeros (with a one indicating a real number). Why?
