Hello, I have calculate in my program the mean value and I am trying to calculate the standard deviaton value of an array 20×20, without using the std command.Next, I compare my result to that whoch I get when I use the std command, but they are different.Could someone explain me the reason? Is their any problem in the types of my algorithm? Here is my code:
mean_value = 65.4250; sum_dev = 0; for i=1:1:20 for j=1:1:20 sum_dev = sum_dev + ((ROI(i,j)- mean_value)^2); end; end; std_dev = ((sum_dev/(40-1))^(1/2)); disp(std_dev); 129.0786 std(ROI(:), 0,1) ans = 40.3552
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