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

Tue Apr 13 04:17:41 CEST 2021

Claus,

> For me the plurality is not so important - but let's say it's the 
> wording used in all our educational books (in English) ... just dig 
> into any Signal Analysis book, etc., and what we're trying to name 
> here is exactly that, then it would be bad for Scilab to give it a 
> different name. Renaming something that is universally defined 
> otherwise is an uphill battle we cannot win.

As I implied earlier, nomenclature could hardly be right or wrong since 
it is mostly arbitrary. But there could be more logical or less logical 
choices.

When it is well established, it is also a battle that is not worth 
fighting, especially if there is some sort of rationale behind it.

> Asymmetric window functions is new to me.I googled about window 
> functions and found (stumbled upon):
> https://journals.sagepub.com/doi/pdf/10.1260/1748-3018.9.4.389

This is another kind of asymmetry. "Periodic" window functions are only 
slightly asymmetric. I don't think they qualify for the kind of windows 
treated in that paper.

Asymmetric windows seem to be a good choice to smooth out the spectrum 
if phase response is not important. Scilab doesn't have any asymmetric 
function, but if a plan to add new windows were approved, they could be 
included along with several more traditional window functions currently 
not covered (such as Blackman, Blackman-Harris or a number of flat-tops).

Symmetric windows are used for FIR filter design. Periodic windows are 
used for spectrum analysis.

Regards,

Federico Miyara

> Conclusion: Asymmetric window functions have a purpose. When there's 
> asymmetric windows, then there must also be symmetric windows.
> Here's a short list of symmetric window functions: 
> https://mathworld.wolfram.com/ApodizationFunction.html
>
> Best regards,
> Claus
>
> On 12-04-2021 17:19, Federico Miyara wrote:
>>
>> Samuel:
>>
>> As a general concept, you are right ... but with nuances. The problem 
>> is deciding when something is really wrong and when it is just a 
>> question of opinion or personal preference. It is wrong to say the 
>> Earth is flat, no matter how many people say it. But is it right or 
>> wrong to call something just a conventional name?
>>
>> For instance: Is it right to call the derivative of a function 
>> "derivative"? Probably not, because "derivative" is a general concept 
>> which seems to have no relationship with its meaning in math. 
>> Probably in its origins it was more related to grammar than to math. 
>> But once established for centuries, it wouldn't be convenient to 
>> change it on the basis that it is "wrong".
>>
>> By the same token, calling "periodic" a window function obtained from 
>> periodic functions (cosines) whose period is equal to its length 
>> doesn't seem intrinsically wrong to me. Calling it "closed" would be 
>> worse since one immediately thinks either of a closed set, which is 
>> not, or a closed curve, which isn't either.
>>
>> But even if we found a better word, changing it would very likely 
>> create an unnecessary cognitive dissonance to thousands or millions 
>> of practitioners.
>>
>> Anyway, if a much better and cristal-clear word (i.e., whose meaning 
>> would be immediately obvious in its context) were found and gained 
>> consensus, no problem to use it instead of "periodic". The important 
>> thing in my proposal was to include in the window() function the 
>> feature, not how we call it.
>>
>> Regards,
>>
>> Federico Miyara
>>
>>
>>
>> On 12/04/2021 04:22, Dang Ngoc Chan, Christophe wrote:
>>> Hello,
>>>
>>>> De : Federico Miyara
>>>> Envoyé : dimanche 11 avril 2021 02:08
>>>>
>>>> Like it or not, I guess these keywords come from Matlab, and as Matlab
>>>> still seems to dominate the market, many people, including those
>>>> willing to quit Matlab (as I did several years ago), are quite used to
>>>> those keywords
>>> I don't agree with this argument.
>>> If a way of doing is wrong, then just keep on going because "everybody does so" is just an argumentum ad populum
>>>
>>> https://en.wikipedia.org/wiki/Argumentum_ad_populum
>>>
>>> which is a fallacious argument.
>>>
>>> Regards.
>>>
>>>
>>> --
>>> Christophe Dang Ngoc Chan
>>> Mechanical calculation engineer
>>>
>>>
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