Path: news.mathworks.com!newsfeed-00.mathworks.com!newsfeed2.dallas1.level3.net!news.level3.com!postnews.google.com!r33g2000yqn.googlegroups.com!not-for-mail
From: Greg <heath@alumni.brown.edu>
Newsgroups: comp.soft-sys.matlab
Subject: Re: FFT
Date: Mon, 6 Jul 2009 22:09:10 -0700 (PDT)
Organization: http://groups.google.com
Lines: 36
Message-ID: <c2daa195-592a-455f-9fa7-b972a1f47cf4@r33g2000yqn.googlegroups.com>
References: <h2eu4q$9h$1@fred.mathworks.com> <496ce8c4-8e49-4b17-9d27-efff652e77ea@b14g2000yqd.googlegroups.com> 
	<h2t6u9$8r0$1@fred.mathworks.com>
NNTP-Posting-Host: 69.141.163.135
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-Trace: posting.google.com 1246943350 26116 127.0.0.1 (7 Jul 2009 05:09:10 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Tue, 7 Jul 2009 05:09:10 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: r33g2000yqn.googlegroups.com; posting-host=69.141.163.135; 
	posting-account=mUealwkAAACvQrLWvunjg50tRAnsNtJR
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 
	2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729),gzip(gfe),gzip(gfe)
Xref: news.mathworks.com comp.soft-sys.matlab:553289


On Jul 6, 11:58 am, "guj " <gulatiaks...@gmail.com> wrote:
> Can any one tell me difference between these notations
>
> Matlab DFT
> for K=1:N
> for n=1:N
> x(w)=sum( n=0 n=N-1) x(n) exp ( 2 pi (k-1) (n-1) /N)

You need to proof read your post. Taken literally,
what you have written is garbage.

Try again.

> NDFT
> for k=1:N
> x(w)=sum( n=0 n=N-1) x(n) exp ( 2 pi freq(k) time(n))

If you do things correctly you should get EXACTLY the same result.
when freq and time are uniformly spaced.

> So here is my question, i was trying to derive the DFT notation of matlab, which is given in help..in that derivation i need to assume that its is equally spaced or my twiddle factor vectors are equally spaced. so DFT notation and NDFT notatin should have some different, also both give different results . DFT Notation of matlab give same result as FFT but NDFT notation give different results

It shouldn't you made a mistake some where.

See my last post in "FFT,IFFT, and NDFT,NFFT "

Hope this helps.

Greg

-----SNIP