How can I create a vector of rolling Standard Deviations
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I'am sure this is an easy question for most of you...
I have a timeseries 'T' and I wanted to convert this into a vector 'V' of rolling Standard deviations. So every element of 'V' is the Std of the previous 30 elements of 'T'. The first thirty elements of 'V' are NaN then, right?
Could someone pleas help me with this problem?
Shashank Prasanna on 21 Jul 2014
It is preferred if you give it a shot first and then seek help,
w = 30;
y = NaN(100,1)
x = randn(100,1);
for ii = w+1:100
y(ii,1) = var(x(ii-w:ii-1,1));
The first 30 need not be NaN, you can make them zero if you prefer.