Combining curves to create a single average curve

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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
  1 Comment
Jan
Jan on 28 Oct 2016
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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Answers (2)

Jan
Jan on 28 Oct 2016
Edited: Jan on 28 Oct 2016
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')
  3 Comments
Khaoula Ouazzani
Khaoula Ouazzani on 28 Mar 2023
@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)?

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KSSV
KSSV on 28 Oct 2016
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')
  2 Comments
Jan
Jan on 28 Oct 2016
This does not consider the detail "the number of and the value of X and Y differs".
KSSV
KSSV on 28 Oct 2016
Numbers can be brought to equal number using interpolation.

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