[PD] variance from mapping library
Mathieu Bouchard
matju at artengine.ca
Mon Mar 23 21:04:22 CET 2009
On Mon, 23 Mar 2009, Mathieu Bouchard wrote:
> You can send simple repeated sequences to [mapping/variance] to show
> that not only it can drift in the negative values almost endlessly, but
> it doesn't even compute the variance of N values. This is because there
> is a moving average of something involving another moving average. This
> makes a global moving average of 2N-1 values instead of N, and then the
> window isn't rectangular anymore, it's triangular, because different
> values are counted different number of times depending on how old they
> are.
errata: i mean that a moving average of a moving average is another moving
average with a different window (the convolution of the two windows), but
the case of [mapping/variance] is more complicated because of the extra
operations being done, and so there is no easy way to describe it, but you
can see that it uses too many values in the same way that the moving
average of the moving average does.
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| Mathieu Bouchard - tél:+1.514.383.3801, Montréal, Québec
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