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Subject: Re: BOX CAR
Date: Wed, 22 Jul 2009 05:24:04 +0000 (UTC)
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ImageAnalyst <imageanalyst@mailinator.com> wrote in message <2121bfee-538d-4585-8c87-6d14651e416c@o36g2000vbl.googlegroups.com>...
> On Jul 21, 2:06?pm, "guj " <gulatiaks...@gmail.com> wrote:
> > ImageAnalyst <imageanal...@mailinator.com> wrote in message <c0146ddf-ae3f-4264-946b-2b85e4ff4...@s31g2000yqs.googlegroups.com>...
> > > On Jul 19, 4:57?am, "Sprinceana " <mihai...@yahoo.com> wrote:
> > > > "guj " <gulatiaks...@gmail.com> wrote in message <h3u671$n0...@fred.mathworks.com>...
> > > > > can any one tell me how can i apply window on my signal which is 296 sample long, i want to see only 64 samples..how can i apply rectangular window...
> >
> > > > > and how to plot it with my funtion
> >
> > > > > I tired RECTWIN(64) but is giving me straight line, and how can i multiply with 296 point signal.
> >
> > > > > I am new to DSP ..:) still learning the things
> >
> > > > You store your 296 sample long on your signal in a variable isn't it?
> >
> > > > So you multiply:
> >
> > > > reactwin(64) *name_of_variable (which consist of your 296 point signal).
> >
> > > > You gave little details a little code and message of errors can guide us to help you quicker!
> >
> > > > Michael
> >
> > > ------------------------------------------------------------------
> > > Yeah, you think that's going to work??? ?The only way to do the
> > > multiplication is if the arrays are the same size, Or multiply just
> > > part of the longer one like this:
> > > a=1:64
> > > b=1:296
> > > c=a .* b(1:length(a))
> >
> > > Or possibly they're thinking about a sliding window sort of thing,
> > > like convolution, conv().
> >
> > > But you're right in that they really haven't given enough information
> > > to give a decent answer.
> > > Regards,
> > > ImageAnalyst
> >
> > Lets ?see it like that
> >
> > I have s which is a spectra signal length a, w another signal spectra of length b when i convolve spectra of both of them i get y=s*w..Now y has length a+b-1.......So for getting s back i need to apply low pass filter...say a rectangular function.....RECTWIN (in matlab)....
> >
> > If i apply some thing like
> > y.*RECTWIN(length(s)) it wont work as they r of not equal size...so how will i apply it..am i clear now ...this question seem to trivial but i dont understand- Hide quoted text -
> >
> -----------------------------------------------------------------------
> Don't use rectwin, and you certainly don't use a low pass filter to
> extract a part of a signal (that would just mess up your convolution -
> change it's shape).  You just use regular indexing.
> For example if you signal is 100 long and your kernel is 11 long, the
> convolution will be 111 long.  If you want the central 100 out of it,
> just say
> sameSizeSignal = convolutionResult(6:105);
> Good luck,
> ImageAnalyst


i think convolution will be 110 in length and genrally when we use funtion like box car to reconsruct a signal back in fourier domain (i am not sure though)