You need to specify the x (SNR) and y (Weight) coordinate for each z-value (error). Since z is a matrix, x and y need to be matricies of the same size.
SNR = repmat([15 30 50]', 1, size(error,2)); %note the transpose
Weight = repmat(0.1 : 0.1 : 0.9, size(error,1),1);
plot3(SNR, Weight, error)
