When you perform mathematical operations on arrays or matrices in MATLAB you need to use syntax which is slightly different than when you are using MATLAB as a calculator.
For example if we define b=[10., 20., 30.] and a=[1., 2., 3.] and then the correct way to add these arrays in MATLAB is b+a but the correct way to multiply them element by element is b.*a, which produces [10., 40., 90.] Note the extra period before the multiply symbol *. If you say b*a, you get an error in MATLAB because the program thinks you want to multiply a 1 by 3 matrix by a 1 by 3 matrix, which is not possible.
There is a similar divide symbol ./ and an exponent symbol .^ . For example, a.^ 2 produces [ 1., 4., 9.].