mathnewbie - the error message is telling you that PeT is undefined. Nowhere in the code have you tried to define this variable until you use it within the following for loop
for i=1:roots
value=value+besselj(1,beta(i)*Ri/R)*besselj(0,beta(i)*r/R)/(beta(i)*(besselj(0,beta(i)))^2)*(z/R)*exp(-beta(i)^2*z/(PeT*R));
end
You will need to initialize this variable before you try and use it... Though this is the same input variable in your anonymous function
modelfun=@(PeT,r)C0*(1+(2*R/Ri)*value);
so you may need to clarify what youa are trying to do. It may be that you want to create a nested function like the following
function myMainFunction
filename='d5D21Re50.csv';
M=csvread(filename,1,0);
d=5e-3; % particle diameter (m)
% etc.
function [x] = myNestedFunction(PeT,r)
value=0;
for i=1:roots
value=value+besselj(1,beta(i)*Ri/R)*besselj(0,beta(i)*r/R)/(beta(i)*(besselj(0,beta(i)))^2)*(z/R)*exp(-beta(i)^2*z/(PeT*R));
end
x = C0*(1+(2*R/Ri)*value);
end
x=lsqcurvefit(@myNestedFunction,12,myArray,radCprof);
end
I haven't tried the above but I hope you get the idea of how your nested function - which has access to all the local variables defined in the main function - can be used for the least squares curve fitting problem...
