How to interpolate an intermediate curve from curves with different number of data points?

Hello

See the attached picture. The picture shows 4 stress-strain curves, each curve is for a different temperature. What I want is to approximate a curve for 60 deg Celsius. How do I do this? I think there will be lots of problems stemming from that each curve stop at a different strain. I have looked at this question ( https://stackoverflow.com/questions/23494254/interpolation-between-two-curves-matlab?fbclid=IwAR1XKpmOxYtRmd1Zibe6zo4hNRNJAXI2NhC8ByFx-V4HmzQ2XiUl9GTn-Vg ) and answer but I dont think it will give me what I want.

[KSSV]

Attach your data...Read about griddata, scatteredinterpolant.

[Henry Eriksson]

Thank you!

I attached the data. I will try what you said and hoping in the meantime that I get some help.

Answer 1

[KSSV]

data = xlsread("Data.xlsx") ; 
t = data(:,1) ; 

strain = data(:,2) ; 
stress = data(:,3) ; 
%
[c,ia,ib] = unique(t) ; 
N = length(c) ; 
x = cell(N,1) ; 
y = cell(N,1) ; 
z = cell(N,1) ; 
for i = 1:N
  x{i} = strain(ib==i) ;
  y{i} = stress(ib==i) ;
  z{i} = t(ib==i) ;
end
% Make all cells to same size and into a matrix 
Y = zeros(N,100) ;
for i = 1:N
  xi = x{i} ; yi = y{i} ; 
  xxi = linspace(x{end}(1),x{4}(end),100) ; 
  yyi = interp1(xi,yi,xxi) ; 
  yyi(isnan(yyi)) = yi(end) ; 
  Y(i,:) = yyi ; 
end
X = repmat(xxi,4,1) ; 
Z = repmat(c,1,100) ; 
% use contour 
contour(X,Y,Z)
colorbar

[Henry Eriksson]

Thank you! I have tested this out and it seems to do about what I want! :D I will understand it a bit more and comment it.