Re: Weighted Moving Average

[James Sherman Jr.]

Its not an octave thing, but a signal processing thing.  An FIR (finite input response) filter is determined by the vector of the coefficients, so if the filter has length 4, the output would be something like:
y(t) = b(1)*x(t) + b(2)*x(t-1) + b(3)*x(t-2) + b(4)*x(t-3)

So when b = ones(1,4)/4;, it is just the average of the last four elements.

In octave, you can use the function "filter" to do exactly that, if x is your signal, you can simply do
y = filter(b, 1, x);

James

P.S. This is almost the same as Søren's suggestion to use convolution (using the conv function).  The only difference (I believe) is that filter will give the same output as conv, but truncated to the length of x.

On 8/10/07, Luca Delucchi <address@hidden> wrote:

2007/8/10, Schirmacher, Rolf <address@hidden>:
> Filter with an FIR filter? Coefficients would be
>
> b = [1 1 1 1] ./ 4
>

What is this? Sorry but I'm a newbie of octave

> HTH,
>
> Rolf
>

Luca

> > -----Original Message-----
> > From: Luca Delucchi [mailto: address@hidden]
> > Sent: Friday, August 10, 2007 9:20 AM
> > To: octave
> > Subject: Weighted Moving Average
> >
> >
> > Hi, I can do a function on Weighted Moving Average where the value are
> > take in automatic mode? this my idea
> >
> > #y=[y1,y2,y3,y4,y5]
> > function wma(y)
> > (y1+2*y2+y3)/4
> > (y2+2*y3+y4)/4
> > etc
> > etc
> > end function
> >
> > I could not repeat the formula (y1+2*y2+y3)/4 (because if the long of
> > vector is different i must change the function) but have only one
> > formula that use the formula for all values of vector
> >
> > I hope I've given a clear explanation
> >
> > Luca
> > _______________________________________________
> > Help-octave mailing list
> > address@hidden
> > https://www.cae.wisc.edu/mailman/listinfo/help-octave
> >
>
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