Detecting maximum with threshold

Question

Hanna Armstrong 2022-11-28

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1864973-detecting-maximum-with-threshold

评论： Matt J 2022-11-28

%example threshold detection code
function [MAXES] = identifyMaximums(Avg) 
X = Avg;
threshold = 30;
[Xon, Xoff] = detectThreshold(X,threshold);
nSteps = length(Xon);
firstOff = 1;
while Xoff(firstOff) > Xon(1)
    firstOff = firstOff+1;
end
lastOn = nSteps;
while Xon(lastOn) > Xoff(end)
    lastOn = lastOn-1;
end
%Adjust ons and offs
Xon_align = Xon(1:lastOn);
Xoff_align = Xoff(firstOff:end);
%Count number of steps after aligning
nStepsFinal = length(Xon_align);
%Initialize matrix of maximums
MAXES = NaN(nStepsFinal,1);
for i = 1:nStepsFinal
    MAXES(i) = max(X(Xon_align(i):Xoff_align(i)));
end
    function [Ons,Offs] = detectThreshold(signal,threshold)
        overThreshold = signal>threshold;
        onOffs = diff(overThreshold);
        
        Offs = find(onOffs==-1)+1;
        Ons  = find(onOffs==1);
    end
end

Error:

Index exceeds the number of array elements. Index must

not exceed 0.

Error in identifyMaximums (line 14)

while Xoff(firstOff) > Xon(1)

Error in load_data_10_15 (line 119)

[MAXES] = mean(identifyMaximums(Avg));

Data (Avg) that is being processed:attached image

Hello I hope all is well. I am currently working on a side project where I am trying to match data from a sensor to a force plate. At the moment I am trying to linearize the data. To do so, I must collect the peak values. For some reason I am getting this error and I am not sure why. If you have the time, please look over my work and provide some guidence.

Thank you!

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Answer 1

Steven Lord 2022-11-28

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1864973-detecting-maximum-with-threshold#answer_1113658

You may want to take a look at the islocalmax function.

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Hanna Armstrong 2022-11-28

Hi Steven, So I did the localmax function and plotteded it and this is what I am getting, do you have any reccomendations in regards to filtering out the bottom values?

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Answer 2

Matt J 2022-11-28

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1864973-detecting-maximum-with-threshold#answer_1113648

编辑：Matt J 2022-11-28

在 MATLAB Online 中打开

If you have the time, please look over my work and provide some guidence.

In detectThreshold(), you need to add control logic to handle the case where find() returns empty [].

Offs = find(onOffs==-1)+1;
Ons  = find(onOffs==1);

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Hanna Armstrong 2022-11-28

Hi Matt, thank you for responding!

If you can, may you please elaborate on what you mean by adding control logic? At the moment I don't understand how I am supposed to change it.

Thanks.

Matt J 2022-11-28

I left it to you because only you knowwhat's supposed to happen when no peaks are detected.

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