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Peak to Peak detection for a vector on a moving window

I have a vector with size (1x300000) lets say.  I wish to detect peak to peak exceptions exceeding a threshold of a certain value over each sliding window of a defined width.  How can I accomplish it without using a for loop.

- Narayana
0
3/7/2012 6:02:13 PM
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"Timothy " <narayanais@hotmail.com> wrote in message <jj87r4$68g$1@newscl01ah.mathworks.com>...
> I have a vector with size (1x300000) lets say.  I wish to detect peak to peak exceptions exceeding a threshold of a certain value over each sliding window of a defined width.  How can I accomplish it without using a for loop.
> 
> - Narayana

doc diff
doc find

Good luck
0
3/10/2012 7:50:26 AM
This is what I have written.  I wanted some help to improve it?


%variables
threshold = 8;
winsize = 5;


% Data
time = 0:0.1:10;
data = rand(size(time))*10;
plot(time,data);

%calculate the peak to peak for the sliding window

peaktopeak = [];
for i = winsize+1:size(data,2)-winsize-1
    peaktopeak = [peaktopeak max(data(i-winsize:i+winsize))-min(data(i-winsize:i+winsize))];
end

% initialize exceptions
exceptions = [];

% find all data points that exceed the threshold
exceptions.is_exception = peaktopeak>threshold
    
% find start and end locations of each exception location
exceptions.switch = [exceptions.is_exception(1:end) 0] - [0 exceptions.is_exception(1:end)];
exceptions.start = find(exceptions.switch > 0);
exceptions.end = find(exceptions.switch < 0) - 1;

% count the number of locations where the threshold is exceeded
exceptions.num_locations = min(length(exceptions.start), length(exceptions.end));

% find the max value in each location and record its location in the dataset
for i = 1:exceptions.num_locations
    [exceptions.value(i,1), exceptions.loc(i,1)] = max(data(exceptions.start(i):exceptions.end(i)));
    exceptions.loc(i,1) = exceptions.loc(i,1) + exceptions.start(i) - 1;
end
0
3/20/2012 6:58:12 PM
On Mar 20, 2:58=A0pm, "Timothy " <narayan...@hotmail.com> wrote:
> This is what I have written. =A0I wanted some help to improve it?
>
> %variables
[code snipped]
> end
--------------------------------------------------------------------------
What is an "exception"?  In computers, that is an error generated by
your code.  Do you mean just that the data exceeded the threshold
value?  And what are "peak to peak exceptions"?

Does your window move by one element as it slides, or does it move in
jumps of the window width (so that you have no overlapping windows)?
You might be able to use imclose() (in the Image Processing Toolbox),
find(), or blockproc() but before I say which I'd need to know better
how you define an exception (not sure I completely follow your code so
a screenshot or explanation in words would be helpful).
0
imageanalyst (7621)
3/20/2012 9:31:50 PM
ImageAnalyst <imageanalyst@mailinator.com> wrote in message <46168307-1545-4711-9a1e-d1499fdcd2bd@wb9g2000pbc.googlegroups.com>...
> On Mar 20, 2:58 pm, "Timothy " <narayan...@hotmail.com> wrote:
> > This is what I have written.  I wanted some help to improve it?
> >
> > %variables
> [code snipped]
> > end
> --------------------------------------------------------------------------
> What is an "exception"?  In computers, that is an error generated by
> your code.  Do you mean just that the data exceeded the threshold
> value?  And what are "peak to peak exceptions"?
> 
> Does your window move by one element as it slides, or does it move in
> jumps of the window width (so that you have no overlapping windows)?
> You might be able to use imclose() (in the Image Processing Toolbox),
> find(), or blockproc() but before I say which I'd need to know better
> how you define an exception (not sure I completely follow your code so
> a screenshot or explanation in words would be helpful).


ImageAnalyst - Thank you for the response.

Exception is the event where data exceeds the threshold value.  Peak to peak value is the difference between the max and min in a particular window and the exception is the event of exceeding the threshold value.  The window only moves by one element so it slides and does not jump.  Jumping is sorta easy using reshape.  

Please let me know if that helps.

Thank you
0
3/20/2012 10:03:28 PM
Do you have the Image Processing Toolbox, so you can use  rangefilt?


rangefilt


Local range of image
Syntax


J = rangefilt(I)
J = rangefilt(I, NHOOD)

Description


J = rangefilt(I) returns the array J, where each output pixel contains
the range value (maximum value - minimum value) of the 3-by-3
neighborhood around the corresponding pixel in the input image I. The
image I can have any dimension. The output image J is the same size as
the input image I.

J = rangefilt(I, NHOOD) performs range filtering of the input image I
where you specify the neighborhood in NHOOD. NHOOD is a
multidimensional array of zeros and ones where the nonzero elements
specify the neighborhood for the range filtering operation. NHOOD's
size must be odd in each dimension.
0
imageanalyst (7621)
3/21/2012 2:30:44 AM
"Timothy " <narayanais@hotmail.com> wrote in message 

At least the peak-to-peak part (supposingly most consuming )can be vectorized using this FEX: http://www.mathworks.com/matlabcentral/fileexchange/24705-minmax-filter

I'm not sure how to vectorize the exception for-loop

%variables
threshold = 8;
winsize = 5;


% Data
time = 0:0.1:10;
data = rand(size(time))*10;
plot(time,data);

%calculate the peak to peak for the sliding window
% for-loop engine
peaktopeak = [];
for i = winsize+1:size(data,2)-winsize % Attention change the loop end index
    peaktopeak = [peaktopeak max(data(i-winsize:i+winsize))-min(data(i-winsize:i+winsize))];
end

% vectorize engine using FEX
[mindata maxdata] = minmaxfilt(data, 2*winsize+1, [], 'valid');
peaktopeak = maxdata - mindata;

% Bruno
0
b.luong5955 (6401)
3/21/2012 6:50:32 AM
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I'm a complete newbie to audio processing but I'm working on a project that requires some audio imaging. The audio files will typically be 30 minute files that average about 256mb. I can graph the whole thing just file but it's slow and uses too much memory. So, I'm hoping to learn how to use peak files to speed up display times. I'm not looking for very detailed information (although that would be wonderful), I'm looking for some pointers on what I need to be watching for and doing. I know the general idea of just graphing the max value of a My main problem is what to do when the user zooms in or out of the audio file. Can anyone give me some pointers, links or book suggestions? I'd really appreciate the help. in article 1111120728.729655.39800@o13g2000cwo.googlegroups.com, seijin@gmail.com at seijin@gmail.com wrote on 03/17/2005 23:38: > So, I'm hoping to learn how to use peak files to speed up display > times. I'm not looking for very detailed information (although that > would be wonderful), I'm looking for some pointers on what I need to be > watching for and doing. I know the general idea of just graphing the > max value of a My main problem is what to do when the user zooms in > or out of the audio file. what do you mean by "peak files"? there's some product line by a company calle "Peak Audio" and you don't mean anything related to them, do you? (it all looks hardw...

Web resources about - Peak to Peak detection for a vector on a moving window - comp.soft-sys.matlab

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