how to calculate variance of a signal after it reaches a steady state value...

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Vidhya Dharshini
Vidhya Dharshini 2013-9-27
评论： Jessica 2015-3-18
The signal for which the variance is to be calculated is in the base workspace in timeseries format. i want to calculate the variance only after 0.5 seconds. How to do it?
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Vidhya Dharshini
Vidhya Dharshini 2013-9-29
yeah.......i can get you.......you mean steady state refers to the property of not changing with time........for my case i am designing a speed controller for a motor......when i set a reference speed of 20000, the speed starts increasing from 0 to 20000. it oscillates around 20000. and i want to calculate the variance only after it reaches my reference value........ i should have mentioned it as desired value instead of steady state value in the question........thank u.......i have calculated the variance.....

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Image Analyst
Image Analyst 2013-9-27
编辑：Image Analyst 2013-9-27
What element does 0.5 seconds occur at? Let's say it's element 42, so then you do
varSteadyState = var(yourSignal(42:end));
Let's say you have a vector t with the times, and a vector yourSignal with the signal value. You can find the index for which t equals or passes 0.5 seconds like this:
startingElement = find(t>=0.5, 1, 'first');
varSteadyState = var(yourSignal(startingElement :end));

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