limiting standart deviation of a signal

Hi all,

i have a really easy question. I need std() command to limit. So i have a signal as name ST (on y axis) and time (on x axis) and time is from 0 to 10 seconds. But i need to find standart deviation of signal just between 0 to 3 seconds. You can see my graph.

I would be very appreciated for your answers. Thanks a lot!

Answer 1

[Adam Danz]

Let's say your time variable is

time = 0:.1:10;

and your data is named 'data'.

First locate all time samples between 0 and 3 sec

idx = time >= 0 & time <= 3;

Then calculate std of your data for those times.

sig = std(data(idx));

This can be done all in 1 line like this

sig = std(data(time >= 0 & time <= 3));

*This assumes your 'time' and 'data' points correspond.