Combining curves to create a single average curve

Question

Dominic Hui 2016-10-27

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https://ww2.mathworks.cn/matlabcentral/answers/309489-combining-curves-to-create-a-single-average-curve

评论： Jan 2023-4-13

Hi, I've got some data from an experiment that has been repeated three times. I'd like to plot the average of the curves. However, for each replicate the number of and the value of X and Y differs. I was wondering what the best approach is for dealing with this? I've tried to interpolate by using a common x scale but run into difficulties was the number of Y vallues differ.

I'm very new to matlab and anyhelp would be greatly appreciated!

Thanks

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Jan 2016-10-28

If you post what you have tried, suggesting an improvement would be much easier and more likely to match your current code.

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Answer 1

Jan 2016-10-28

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https://ww2.mathworks.cn/matlabcentral/answers/309489-combining-curves-to-create-a-single-average-curve#answer_241114

编辑：Jan 2016-10-28

在 MATLAB Online 中打开

Interpolation is the correct approach:

% Test data:
x1 = linspace(0, 2*pi, 100);
y1 = sin(x1) + rand(size(x1)) * 0.2 + 0.1;
x2 = linspace(0, 2*pi, 110);
y2 = sin(x2) + rand(size(x2)) * 0.2;
x3 = linspace(0, 2*pi, 120);
y3 = sin(x3) + rand(size(x3)) * 0.2 - 0.1;
% Interpolate to get same time resolution:
x   = linspace(0, 2*pi, 200);
yy1 = interp1(x1, y1, x);
yy2 = interp1(x2, y2, x);
yy3 = interp1(x3, y3, x);
y   = mean([yy1; yy2; yy3], 1);
axes('NextPlot', 'add');   % as: hold on
plot(x1, y1, 'r', x2, y2, 'g', x3, y3, 'b', x, y, 'k')

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Khaoula Ouazzani 2023-3-28

@Jan thank you for the information (eventhough I read it years later lol).

I have anoter question: what if my data has got different xi (I can't interpolate relatively to one X)?

Jan 2023-4-13

@Khaoula Ouazzani: Can you give an explicit example?

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Answer 2

KSSV 2016-10-28

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https://ww2.mathworks.cn/matlabcentral/answers/309489-combining-curves-to-create-a-single-average-curve#answer_241093

在 MATLAB Online 中打开

clc; clear all ;
t = linspace(0,2*pi) ;
x1 = 0.1*sin(t) ;
x2 = 0.15*sin(t) ;
x3 = 0.2*sin(t) ;
% 
hold on
plot(t,x1,'r') ;
plot(t,x2,'b') ;
plot(t,x3,'g') ;
%%calculate average 
xavg = (x1+x2+x3)/3 ;
plot(t,xavg,'k')