[Scilab-users] Why window() provides only symmetric weighting?

[Samuel Gougeon]

Dear Federico,

Thank you for the proposal.
I am afraid that the "symmetric" and "periodic" flag names are not 
intuitive to me.
Indeed, the generated window is /always/ both periodic and symmetric. It 
is anyway "algorithmically seen" as periodic (from a spectral point of 
view), since it is regularly sampled, while regular-sampling and 
periodicity are FT-dual.

The point is that it is either *open*, or *closed* (what is rather 
expected, for a window. Sorry for the (serious) joke :-), with a closing 
point at the same level as the opening one.

I know from where these "symmetric" and "periodic" keyworks come from.
But, sorry, i can't resolve myself blindly copy others without 
discussion. Badly naming things usually become counterproductive, 
noticeably when teaching (here signal processing).

For contribution,

Best regards
Samuel


Le 11/02/2021 à 08:12, Federico Miyara a écrit :
>
> Dear All,
>
> I wonder why windowing functions such as Hann, Hamming, etc., provided 
> by window(), are only symmetric.
>
> When used for spectral analysis by subsequent use of fft(), the 
> periodic weighting is better than the symmetric one. The symmetric 
> window is mainly used in the design of FIR filters, which I guess is a 
> less frequent application than spectral analysis.
>
> While it is true that an easy workaround to get a periodic window of 
> length n is, for instance
>
> w = window("hn", n+1)(1:$-1);
>
> a syntax such as this
>
> w = window("hn", n, "per");
>
> would be easier.Setting "sym" as the default option, no backward 
> compatibility issues would possibly arise.
>
> Regards,
>
> Federico Miyara
>
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