Mine

function [noisy_face] = create_noise (face, percent)

%

max_colour_value = 255;
total_pixels = 972;

% number of pixels to change
num_pixels = uint8 (total_pixels * percent);

% random value sets, one for random indices and one for random values
rand_values_index = rand (num_pixels, 1);
rand_values_mag = rand (num_pixels, 1);

% copy old face to new face
noisy_face = face;

for i = 1:num_pixels
    change_index = uint8 (rand_values_index (i) * total_pixels);
    
    if change_index < 1
        change_index = 1;
    end
    
    if change_index > total_pixels
        change_index = total_pixels;
    end
    
    noisy_face (change_index) = rand_values_mag (i) * max_colour_value;
end