Help with Cross-correlation and Auto-correlation

Question

David Jones 2021-6-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/865725-help-with-cross-correlation-and-auto-correlation

评论： David Jones 2021-6-30

Raw_Data.mat

Hi

I don’t have that much experience in MATLAB, I hope someone can point me in the right direction, I am looking at breathing and the rate and various ways to detect this. I am currently looking into Cross correlation and auto correlation can somebody please help me setup some basic code and give me a few pointers.

I have attached a file which has 6000 samples, 100 samples per second, over 60 seconds.

Any help would be greatly appreciated.

Kind Regards

David

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Answer 1

Image Analyst 2021-6-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/865725-help-with-cross-correlation-and-auto-correlation#answer_734240

在 MATLAB Online 中打开

Raw_Data.mat

Try this:

s = load('raw_data.mat')
y = s.raw_ad_data_sine;
plot(y, 'b-', 'LineWidth', 2);
grid on;
% Find peaks
[peakValues, indexesOfPeaks] = findpeaks(y, 'MinPeakDistance', 200, 'Threshold', 1000);
% Plot them.
hold on;
plot(indexesOfPeaks, y(indexesOfPeaks), 'rv', 'LineWidth', 2, 'MarkerSize', 10);
% Find valleys
[valleyValues, indexesOfValley] = findpeaks(-y, 'MinPeakDistance', 200, 'Threshold', 1000);
valleyValues = -valleyValues;
% Plot them.
hold on;
plot(indexesOfValley, y(indexesOfValley), 'r^', 'LineWidth', 2, 'MarkerSize', 10);

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Image Analyst 2021-6-28

在 MATLAB Online 中打开

Raw_Data.mat

David, you will just have to try different amounts of data smoothing and parameters to find something that works. There are lots of parameters in sgolayfilt() and findpeaks() and I don't have the time to do the trial and error to optimze them for you. I'll leave that to you but I think you have a start anyway.

% Demo by Image Analyst.
clc;	% Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);
close all;	% Close all figures (except those of imtool.)
clearvars;
workspace;	% Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
s = load('raw_data.mat')
y = s.raw_ad_data_sine;
plot(y, 'c.');
% Smooth the data with a Savitzky-Golay filter.
windowWidth = 291;
y = sgolayfilt(y, 4, windowWidth);
hold on;
plot(y, 'b-', 'LineWidth', 2);
grid on;
caption = sprintf('Data smoothed with Savitzy-Golay filter of width %d', windowWidth);
title(caption, 'FontSize', fontSize);
drawnow;
% Find peaks
fprintf('Finding peaks...\n');
[peakValues, indexesOfPeaks] = findpeaks(y, 'MinPeakDistance', 100);
if isempty(peakValues)
	fprintf('No peaks found with those parameters.  Try adjusting the parameters.\n');
else
	% Plot them.
	fprintf('Plotting peaks...\n');
	hold on;
	plot(indexesOfPeaks, y(indexesOfPeaks), 'rv', 'LineWidth', 2, 'MarkerSize', 10);
	drawnow;
end
% Find valleys
fprintf('Finding valleys...\n');
[valleyValues, indexesOfValley] = findpeaks(-y, 'MinPeakDistance', 100);
valleyValues = -valleyValues;
if isempty(peakValues)
	fprintf('No valleys found with those parameters.  Try adjusting the parameters.\n');
else
	% Plot them.
	fprintf('Plotting valleys...\n');
	hold on;
	plot(indexesOfValley, y(indexesOfValley), 'r^', 'LineWidth', 2, 'MarkerSize', 10);
end
g = gcf;
g.WindowState = 'maximized'
fprintf('Done running %s.m\n', mfilename);

Image Analyst 2021-6-29

在 MATLAB Online 中打开

Not sure what that means but you can create an x axis if you want with linspace. If the total length of y is 60 seconds, you can make x like

x = linspace(0, 60, length(y));

David Jones 2021-6-30

Results.fig

Hi

I am strugling to get the display to show the 60s of data correctly, please see atached display I need to display the last graph (5) with the x axis showing the correct timimng , could you please help.

David

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