Stack Exchange
log in

Peter K.

 Post-Processing

General discussion for dsp.stackexchange.com
1
Peter K.
Jun 23 21:56
@Randy Not at all. The up and down votes are completely anonymous. Even the mods can't see who has voted how.
Peter K.
Jan 22, 2023 19:15
I’ve gone onto mobile for now. Will check it out once I’m back at my desk.
Peter K.
Jan 22, 2023 18:41
OK, I think I've made an appropriate pull request. github.com/tripleee/sloshy/pull/39
Peter K.
Jan 22, 2023 18:28
No worries. Just looking at doing a PR now... will let you know if I figure it out. :D
Peter K.
Jan 22, 2023 18:24
@n00dles You rang? What's up?
Peter K.
Jun 23, 2021 22:46
user image
Peter K.
Jun 23, 2021 22:46
@Royi Still looks OK to me.
Peter K.
Jan 6, 2021 14:07
@Royi Done! Thanks for the heads-up.
Peter K.
Sep 7, 2020 18:25
Interesting! Where I've come across such patterns is when lighting is modulated. Most fluorescent lights are really poor for even lighting because they "flash" at the mains frequency unless you get the more expensive high frequency ones. Even those flash, they just do so at a frequency that's higher than noticeable to humans. I used to have to run my old CRT computer monitors at 75Hz or greater. Otherwise I'd get a headache from the 50 to 60 Hz refresh rate. :-)
 

 Discussion on answer by TheDemonLord:…

Imported from a comment discussion on workplace.stackexchange....
Peter K.
May 22, 2024 22:51
@Questor Bad analogy. The login violators have agency, as does the violated. The weather does not.
Peter K.
May 22, 2024 22:51
@Questor You're still blaming the victim.
Peter K.
May 22, 2024 22:51
Arguably victim-blaming, but that doesn't mean it's not also true. +1
 

 Discussion on question by centauri: C…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
May 13, 2024 17:00
@centauri Tell me something I do not know.
Peter K.
May 12, 2024 16:26
OK, but even those variable resistors are not really varying instantaneously. Short-term, they're linear.
Peter K.
May 12, 2024 15:58
I'm not sure what you mean by a non-linear inductor or capacitor or resistor? It's not an inductor, capacitor or resistor if it's non-linear.
Peter K.
May 12, 2024 15:58
But circuits containing only inductors, capacitors, and resistors are linear.
Peter K.
May 12, 2024 15:58
Right, but the case of an inductor (or capacitor) isn't time-varying or non-linear. Can you edit your question to give an example of a system you're trying to analyze? Or link to somewhere that shows it?
Peter K.
May 12, 2024 15:58
So, I wonder why the frequency domain is needed to calculate impedance? If I have $v(t)$ and $i(t)$, isn't it just $z(t) = \displaystyle \frac{v(t)}{i(t)}$ ?
Peter K.
May 12, 2024 15:58
Welcome to SE.SP! I'm struggling to understand what is meant by impedance in this instance (time-varying and non-linear). It it at all a useful concept? I'm seeing that it might come from the power industry or perhaps robotics. Can you give a definition that you use?
 

 Discussion on question by AChem: How …

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
Feb 7, 2024 17:09
Interesting paper! I'm intrigued that it's possible to miss peaks. That's probably possible in standard uniform sampling, but the example given in the paper seems particularly bad (or good, depending on which way you look at it).
Peter K.
Feb 7, 2024 15:05
Interesting? Looks like a preprint is available here: arxiv.org/pdf/1703.09824.pdf
Peter K.
Feb 7, 2024 14:32
OK. See if that makes sense to you. I think I've captured what you're asking, but I am willing to be corrected. :-)
Peter K.
Feb 7, 2024 14:24
OK! That makes sense. Let me take a stab at editing the question and see if that matches what you're thinking.
Peter K.
Feb 7, 2024 13:51
I think I'm starting to get what is being asked, but it's not clearly stated so far (for me).
Peter K.
Feb 7, 2024 13:50
And, that is different from the question in the title.
Peter K.
Feb 7, 2024 13:50
What I'm confused about is the statement I would like to make make a uniformly spaced frequency axis versus the statement will this frequency axis scaling remain valid depending on the type of sampling. They're two different things?
Peter K.
Feb 7, 2024 13:48
Now I'm completely unsure what is being asked. Please edit the question and clarify.
Peter K.
Feb 7, 2024 13:48
The Matlab page linked to gives the code: Y = nufft(X,t); n = length(t); f = (0:n-1)/n; plot(f,abs(Y)) which clearly sets the frequency axis as uniformly sampled.
Peter K.
Feb 7, 2024 13:48
But isn't that what the Matlab function does by default? What do you mean by an "accurate frequency axis"?
Peter K.
Feb 7, 2024 13:48
Is something other than a uniform frequency grid required? Usually, one needs a uniform grid in frequency.
 

 Discussion between KaBe2003 and tobalt

Imported from a comment discussion on electronics.stackexchang...
Peter K.
Jun 6, 2023 13:39
Sorry, I don't have anything to add.
 

 Discussion between Dan Boschen and Ba…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
Jun 2, 2023 13:21
Yes. That was my meaning.
Peter K.
Jun 2, 2023 13:19
It was very poorly worded at the start. Thank-you for your patience, @Barzi2001.
Peter K.
Jun 2, 2023 13:18
I should have just deleted the comments at the start and moved them here. I'll do that immediately in future.
Peter K.
Jun 2, 2023 13:17
The reason I removed the comments was because I was trying to stop the post from being flagged with too many comments. I felt your deleted comments had been acted on and no longer relevant.
 

 Discussion on question by Volpina: Ca…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
May 29, 2023 19:55
However, since the 𝑡 part is completely separable from the 𝑡0 part,... seems to be very restrictive. It is not generally the case that a function of two variables is separable.
 

 Discussion on answer by robert bristo…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
May 24, 2023 17:15
In case you want to go into all the other logical (and illogical) ways of "proving" something, here's what I consider to be the canonical list: users.cs.northwestern.edu/~riesbeck/proofs.html
 

 Discussion on question by Rubem Pacel…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
Nov 6, 2022 22:17
@RubemPacelli I thought your post was great. I knew it'd prompt discussion. But my reading of it is that you went uncivil first and kept at it. That is an indication that something is wrong. I'd like to get to the bottom of the issue in your question. I just want to get their civilly. You, it seems, do not.
Peter K.
Nov 6, 2022 20:49
All very interesting, but do you have a question? I'd need to see more about the definition of $S_x$ and $S_{x_l}$, too.
 

 Discussion between Major Anarchy and …

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
May 18, 2022 18:49
i.e. you have aliasing, unless you know that the signal is bandlimited in some specific way.
Peter K.
May 18, 2022 18:48
So in the range -10Hz to 10Hz, the only peaks you'll see are at -9Hz and +9Hz.
Peter K.
May 18, 2022 18:48
The -19Hz negative copy will put peaks at -19Hz - 10Hz and -19Hz +10Hz.
Peter K.
May 18, 2022 18:47
So the +19Hz positive copy will put peaks at 19Hz - 10Hz and 19Hz + 10Hz.
Peter K.
May 18, 2022 18:46
And sampling has the effect of putting copies of that spectrum every sampling frequency length.
Peter K.
May 18, 2022 18:46
Well... a real-value signal of frequency 10Hz will have peaks at 10Hz and -10Hz.
 

 Discussion between Curious and Dan Bo…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
Nov 30, 2021 13:34
I always liked seeing wagon wheels in movies: youtube.com/watch?v=6XwgbHjRo30
 

 Discussion on question by FabioSpaghe…

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
Nov 30, 2020 16:27
And you're failing to read the responses: this is not what you should expect to see. Why do you expect to see it? And being rude to one of the moderators is not a good way to get your question answered.
Peter K.
Nov 30, 2020 15:04
I closed the question, because there seems to be a fundamental disconnect between what the abs(fft(x)) does and what @FabioSpaghetti is expecting to see. Can you please explain what you're expecting? The magnitude spectrum you posted (both of them) look close to what I would expect: your signal has a DC (zero frequency) component, and that swamps everything else.
 

 Discussion on answer by Dan Boschen: …

Imported from a comment discussion on dsp.stackexchange.com/qu...
Peter K.
May 14, 2020 14:21
@LearningDSP Perfectly OK! Just trying to (gently) let people know about the what SE wants this to work.
Peter K.
May 14, 2020 12:24
@DanBoschen Sorry for the hassle! Sometimes when the "more than 20 comments" flag is thrown, it's because there's an argument. Usually on SE.SP that's not the case.