st: filters in stata

["Juliusz =?utf-8?B?SmFixYJlY2tp?=" <juliusz.jablecki@student.uw.edu.pl>]

Hi everyone, 
I was wondering if you could help me with constructing a moving-average type 
of filter in Stata. Say I have a time series X_t and I want to smooth it in 
the following way: 
X_t(b)=[1-b/1+b]*[\sum(k=-inf/inf)b^|k|*X_(t+k)], 0<b<1 
That is, X_t(b) is supposed to be a moving average with weights declining as 
we move away from the center (the idea is borrowed from Robert Lucas's paper 
"Two Illustrations of the Quantity Theory of Money"). How do I go about this 
problem? 
Thanks,
Juliusz
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