Adding a standard deviation to the equation

Hi,I'm trying to find the standard deviation from this function code that I've written for my mean, please how do I adjust it in order to find the standard deviation from the code I have written? I've tried a few codes but its not running.

function [ret] = mymean(a)
%UNTITLED Summary of this function goes here
%    Detailed explanation goes here

len = length(a);
store=0;

for i=1:len
    store=store+a(i);
end

ret = store / len;

end

Answer 1

[NISARGA G K]

I understand you want to find standard deviation of the vector. Add the following line to your code to obtain the same

standard_deviation = sqrt(sum((a - ret).^2)./(len-1))

Alternately, you can use mean and std functions in matlab