MATLAB: Standard deviation in errorbar

errorbarstandard deviation

[a very silly question!] How to calculate the errorbar with 2 standard deviations in this example?
x=1:10;
y=rand(10,50);
errorbar(x, mean(y,2), std(y,[],2)) % 1 standard deviation
Just multiplying std by 2 in the errorbar, right?
errorbar(x, mean(y,2), 2 * std(y,[],2))

Best Answer

Not silly at all, however it may not produce the result you want.
It might be more appropriate to calculate the errors as the standard error of the mean (S.E.M.) : 
err = 2*(std(y,[],2)/sqrt(size(y,2)));                  % 2 x Standard Error Of The Mean
then: 
figure
errorbar(x, mean(y,2), err) % 2 standard errors of the mean
rather than the standard deviation of the observations themselves.
Related Question