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From: aasim Azooz on 5 Mar 2010 04:26
"Ravi Rastogi" <raviras(a)gmail.com> wrote in message <hmoq29$d07$1(a)fred.mathworks.com>...
> Hi Everyone,
>
> For my application i need to find out the Local Maxima and Minima of the any 1D data.
> Here are the steps:
> 1) Load the data; (Bx)
> please email me and i will send you the data.
>
> 2) Determine the possible no of scales.
>
> %%Determining the maximum scale:
> for p=1:20
> if((2^p)<=(length(Bx)/2))
> maxscl=2^p;
> elseif((2^p)>=(Bx/2))
> break;
> end
> end;
>
> 3) Determine continuous wavelet transform coefficients for all the possible scales
>
> %%Continuous Wavelet Transform:
> scale=1:maxscl;
> space=1:length(Bx);
> figure;
> r=cwt(Bx,scale,'db10','plot');
>
> 4) Use the Localmax function of wavelet toolbox to find and plot all the Local Maxima
> plots.
>
> %%Determining Local Maximum of a MATRIX:
> local_max_coef = localmax(r);
> [Rows, Cols]= find(local_max_coef);
> %Plot the maxima
> figure;
> plot(space(Cols),scale(Rows), ...
> 'marker','*', ...
> 'markersize',2, ...
> 'linestyle','none', ...
> 'color','k');
>
> 5) Then i use a function called peakdet.m ( http://www.billauer.co.il/peakdet.html ) to determine the local max and minima points.
>
> %%Plotting scale space plot of maxima and minima
> max_r(scale,space)=0;
> min_r(scale,space)=0;
> for scl=1:maxscl
> [maxtab, mintab]=peakdet(r(scl,:), 1); % Determining maxima and minima
> maxpos=round(maxtab(:,1)); %position of maxima in space
> max_r(scl,maxpos)=1;
> minpos=round(mintab(:,1));
> min_r(scl,minpos)=1;
> end;
>
> %Plotting it:
> figure;
> imshow(~max_r);
> title('Maxima Plot')
> figure;
> imshow(~min_r);
> title('Minima Plot')
>
> PROBLEM: I want get a plot similar to step 4, but am not sure what is the best way to do it? so i tried out it in matrix and plotting the image, but since the matrix starts from (0,0) on the top left the whole plot looks inverted. Can someone suggest me a better way of plotting the data??
>
> Thanks,
> Ravi

See my M-files Maxima and minima on the matlab file exchange library
Aasim Azooz
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