Smooth the data and find major peaks

Question

Megha 2018-12-19

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评论： Luna 2018-12-26

采纳的回答： Luna

matlab.mat

I have attached a data which shows some periodic peaks.

Upon close observation, it can be found that the data is not continously increasing

or decreasing over a period of sinusodal curve. The data breaks after every several interval.

Can anybody help me smootheing the data and find major increasing and decreasing peaks?

I used several functions like

x2 = smooth(x1);

x2 = smoothdata(x1,'gaussian',20);

x2 = smooth(x1,'loess');

There are still errors and I cannot observe peaks.

Can anyone please help.

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Adam 2018-12-19

在 MATLAB Online 中打开

If you have the SIgnal Processing Toolbox then

doc findpeaks

can help find the peaks.

I don't know what you mean by 'there are still errors' though. There are numerous ways to smooth data, it depends on the data and what is noise and what is true data that should be retained. I have sometimes used Savitzky–Golay filters for this, but gaussian smoothing or even mean smoothing can work depending how aggressive you need the smoothing to be.

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Answer 1

Luna 2018-12-20

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编辑：Luna 2018-12-20

在 MATLAB Online 中打开

findpeaks is built-in function of Matlab and it already works for detecting peaks and locations. Try below:

load('matlab.mat');
y1 = GGG1_qzss;
x1 = (1:numel(y1))'; % creates a time series for 1 seconds each you can use different time samples also 
figure;
plot(x1,y1,'r');
hold on; 
MPH = 8; % minimum peak height you can change it if you want
MINW = 100; % minimum peak width 
[pks,locs]  = findpeaks(y1,x1,'MinPeakHeight',MPH,'MinPeakWidth',MINW);
% pks: peak values
% locs: location of peaks in array
plot(x1(locs),pks,'bo');

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Megha 2018-12-26

@ Luna,

Thank you it worked for me.

Luna 2018-12-26

Your welcome :)

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Answer 2

Sarah Crimi 2018-12-19

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编辑：madhan ravi 2018-12-19

There is an open source function called peakdet.m. Using this function, you have to set the delta which determines what is a peak. For instance when I used this,

delta1=0.000005;

[max_m, min_m]=peakdet(m, delta1);

The link the open source file is below:

https://www.mathworks.com/matlabcentral/fileexchange/47264-peakdet