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Re: peak detection and analysis
Posted:
Mar 10, 2011 10:59 AM
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Hi,
Can you please guide me on how to design a FIR filter for peak detection in a set of images and plotting it out. (MATLAB)
It would be of a greater help.
My input pictures with Laser stripe
https://picasaweb.google.com/lh/sredir?uname=v.navaneethakannan&target=ALBUM&id=5579922441378566865&authkey=Gv1sRgCNCYsYik8c7obQ&feat=email
Kindly help me out.
Thanks,
VJ
"Miroslav Balda" <miroslav.nospam@balda.cz> wrote in message <fegpag$eg8$1@fred.mathworks.com>...
> Paul <gtrpaul@gmail.com> wrote in message
> <1191956217.659229.117090@g4g2000hsf.googlegroups.com>...
> > On Oct 5, 5:22 pm, "Paul Mennen" <nos...@mennen.org> wrote:
> > > Paul <gtrp...@gmail.com> wrote in message
> > > > Megan,
> > > > this is a simple function for a single vector peak
> > > > analysis. It outputs the index (position) into the
> > > > array of the location of all local minima or maxima.
> > >
> > > You have to be careful with a function that simple
> > > especially if your data has limited precision. For
> > > example suppose your data looks like:
> > >
> > > d = [4 5 6 8 8 7 5 2 1];
> > >
> > > You would hope to find a local max somewhere, yet
> > > your function says that there are none. If your data
> > > has lots of bits, you probably don't have to worry
> > > about this.
> > >
> > > I've written some a complicated functions that
> > > attempts to deal with this and other similar situations.
> > > I'll share it you want it, however I just had a thought
> > > of another method. How about low pass filtering the
> > > data slightly. Maybe an FIR filter such as:
> > > [1.0 0.99999]. The slight asymmetry is to deal with
> > > an input such as [4 5 6 8 8 6 3 1].
> > >
> > > ~Paul Mennen
> >
> > Good point, Paul...I make a fundamental assumption that
> neighboring
> > values will treat the first as the peak/trough. In seismic
> data (what
> > I used this on), this is rarely an issue, but something to
> watch out
> > for.
>
> There are several functions in file exchange which might
> help you to solve the issue. I have build the function extr
> which is in FEX under Id 10272. Position of extremes is
> determined by logical array, say L, provided a call is made as
> L=extr(x);
> xmax=x(L{1}); % all maxima
> xmin=x(L{2}); % all minima
> dTmax=diff{xmax); % number of sampling periods
> % between positive extrems
> dTmin=diff(xmin); % ditto for negative extrems
>
> I hope that it helps.
> Mira
>
>
>
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