How can I calculate the standard deviation for a part of "all data"?

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Max Behr 2020-6-1

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评论： Max Behr 2020-6-2

采纳的回答： Image Analyst

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Hello,

I have a two different matrices:

time=[0,0.5,2,4,6]
time =
         0    0.5000    2.0000    4.0000    6.0000
data=[1,3,5,3,6]
data =
     1     3     5     3     6
         

Now I would like to do a specific operation only if time>=0 & =< 4. So in this case only for the first four values of data.

For example these kind of operations:

sqrt(mean((diff(data).*diff(data))))
std(a)

How can I do the calculation only for a specific period of time?

Thanks for your help!

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采纳的回答

Image Analyst 2020-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/540019-how-can-i-calculate-the-standard-deviation-for-a-part-of-all-data#answer_444483

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I have no idea what "a" is. But is this something like you were looking for?

timeVec = [0,0.5,2,4,6] % Don't use "time" since it's a built-in function.
data=[1,3,5,3,6]
indexes = timeVec >= 0 & timeVec <= 4
dataToUse = data(indexes)
% Now do your operation:
result = sqrt(mean((diff(dataToUse) .* diff(dataToUse))))
result2 = std(result) % No idea what a is.  Is it the result of the sqrt() operation?