DFT for Irregular samples
in [Matlab]
|
Prev: add_block for name of Blockset with SPACES??!!
Next: come and join www.pakdub.com a social network with full features like games, classifieds, forums, blogs and a lot more
From: kk KKsingh on 21 Feb 2010 15:11 K will do it Thanks kk TideMan <mulgor(a)gmail.com> wrote in message <b7b3ee88-4946-42a2-91d1-328af827d3f8(a)v20g2000prb.googlegroups.com>... > On Feb 22, 6:10 am, "kk KKsingh" <akikumar1...(a)gmail.com> wrote: > > http://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/PIRODDI1/NUFT... > > > > This is information i got for NDFT and it is sample as what i am trying to code only addon is the factor deltat_n which is known as Riemann sum apprach why dont you give a try and code it may be i will be satisfied if it didnt work for u too > > > > Rune Allnor <all...(a)tele.ntnu.no> wrote in message <688e9a23-a71f-4ed1-b97c-67b5b105d...(a)f29g2000yqa.googlegroups.com>... > > > On 21 Feb, 09:32, "kk KKsingh" <akikumar1...(a)gmail.com> wrote: > > > > I am just trying to code a algorithm, I read in Paper ! > > > > > Don't read the papers. Read the textbooks. > > > > > If the paper is old, then the recent textbooks will present > > > the same material with more easy-to-follow structure and > > > simpler language. > > > > > If the paper is recent, then the authors either don't know > > > that the material is textbook - which in turn means they > > > don't know what they are talking about - or they assume > > > that the reader already know the textbooks. > > > > > Either way: Read the textbooks. > > > > > Rune > > What you don't seem to realise is that while this is new for you, for > many of us, it is old hat. We've been doing it for years. So we > know, without having to prove it to ourselves or you. And we learnt, > not by continually bugging others, but by knuckling down and figuring > it out for ourselves, using textbooks. > > You've posted 30 or so messages this month on this subject. > It's time you did some work for yourself instead of continually asking > questions and expecting others to do your work for you.
From: kk KKsingh on 22 Feb 2010 14:05 Thanks my codes r working now ! But still working only for uniformly sampling not for non uniform samples Rune Allnor <allnor(a)tele.ntnu.no> wrote in message <5d7ebc5d-3058-4b6d-b196-fe0eacbe02d9(a)b7g2000yqd.googlegroups.com>... > On 21 Feb, 18:00, "kk KKsingh" <akikumar1...(a)gmail.com> wrote: > > Ok! But it will be great if u can refer some book too! > > I'll do better than that; I'll mention two: > > Oppenheim and Schafer: Digital Signal Processing (1975) > Papoulis: The Fourier Integral and its Applications (1961) > > Your local academic library will have a copy of each. > One just needs to know that a 'library' is a collection > of 'books'. And how to use the books. And what to use > them for. > > Rune
From: kk KKsingh on 23 Feb 2010 11:12 Hello sir, I have gone through chapters of book you told me. I can easily write a code for uniform sampling and it is giving me correct results. But when i started writing for non uniform sampling, I am getting error. Following problems are comming 1. X(f) = sum(k=1,N){ deltat *x(k) * exp(-2*pi/max(t)-min(t)*j*t(k)*m } deltat=t(n+1)-t(n-1)/2 t(0)=(t(N)-Period)) t(1)=(t(1)+Period)) Now when I take frequency axis as 2*pi/N results are fine but when i make it according to fourier theory 2*pi/(b-a) it is giving me wrong results..For NDFT i was follwing this article http://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/PIRODDI1/NUFT/node4.html and deltat concept came from one of the paper, I didnt get it in book. Now since, you were always pointing out that i am making mistake in DFT basics. it will be great if you can point it out Thanks kk Rune Allnor <allnor(a)tele.ntnu.no> wrote in message <24738d11-bf6b-4a3f-98b4-3c25d8fbd791(a)z35g2000yqd.googlegroups.com>... > On 21 Feb, 01:51, "kk KKsingh" <akikumar1...(a)gmail.com> wrote: > > Just wondering any body has written DFT for the irregular samples...I wrote a code but its wrong some where ! > > > > DFT for irregular samples are based on Reinmann sum method where instead of multiplying with dt we multiply we dt=t(n+1)-t(n-1)/2 and use original sample location t(n) > > Plain wrong. I don't know what a 'Reinman sum' is, but I assume > you might have misspelled the name 'Riemann'. Now, like it or not, > but that's the kind of trivial mistake, blunder, flaw - call it > what you want - that has proved to be typical of your efforts. > > > I apologise if you think that its a trivial problem! But i tried a lot to solve this > > It *is* a trivial problem. You only need to understand what you > are doing. But it's utterly totally essential that you *do* > understand the basics. > > Rune
From: Rune Allnor on 23 Feb 2010 11:29 On 23 Feb, 17:12, "kk KKsingh" <akikumar1...(a)gmail.com> wrote: > Hello sir, > > I have gone through chapters of book you told me. I can easily write a code for uniform sampling and it is giving me correct results. > > But when i started writing for non uniform sampling, I am getting error. Following problems are comming As I said, consult the more recent literature to get the clear, concise expositions. The first two books, from 1961 and 1975, were meant to indicate what time scales are involved when I talk about 'old' and 'recent' literature. The stuff you are looking for can be found in the 1992'ish edition of the book by Proakis and Manolakis. But again: You need to know what you are looking for to find it. Make sure you understand the reguular sampling case in minute detail! Rune
From: kk KKsingh on 23 Feb 2010 11:59
Can you give me your comments on the below :) Both give same results when sampling is uniform m=-M:M N=2M+1 For Regular sampling ( Correct results) for k=1:length(m) freq = (-j*(2*pi/(N))*(k-1)); Wnk = exp(freq.*(0:length(t)-1)); X(k)=Ts*sum(y.*Wnk); end For Irregular Sampling (Incorrect results when i make sampling non uniform, it gives me correct result when its uniform) m=-M:M N1=2M+1 deltak=2*pi/(max(t)-min(t)) for k=1:N1 freq = (i*(deltak)*(k-1)); Wnk = exp(freq.*(t)); X1(k)= sum(yHalf.*Wnk.*deltat(k)); end And, I will surely get the book told by you from libray. Thanks Rune Allnor <allnor(a)tele.ntnu.no> wrote in message <864874f1-eeb7-45b5-b261-6f9e5dee524e(a)g23g2000vbl.googlegroups.com>... > On 23 Feb, 17:12, "kk KKsingh" <akikumar1...(a)gmail.com> wrote: > > Hello sir, > > > > I have gone through chapters of book you told me. I can easily write a code for uniform sampling and it is giving me correct results. > > > > But when i started writing for non uniform sampling, I am getting error. Following problems are comming > > As I said, consult the more recent literature to get the > clear, concise expositions. The first two books, from 1961 > and 1975, were meant to indicate what time scales are involved > when I talk about 'old' and 'recent' literature. > > The stuff you are looking for can be found in the 1992'ish > edition of the book by Proakis and Manolakis. > > But again: You need to know what you are looking for to > find it. Make sure you understand the reguular sampling > case in minute detail! > > Rune |