MATLAB: Fit curves to data

curve fitting

Hello!
Assume that I have this code:
u0 = pi*4E-7;
I = 5;
N = 1;
X = [ 12.0 ; 8.5 ; 6.0 ; 4.1 ; 3.5 ];
B1 = [ 0.03 ; 0.05 ; 0.1 ; 0.2 ; 0.35 ];
B2= [ 0.07 ; 0.07  ; 0.15 ; 0.24 ; 0.32];
Bex= (B1 + B2)/2;
Bth= 1E5*u0*I*N./(X);
plot(X,Bex,'bo',X,Bth,'r^');
Now, I want to curves to fit data, and their equations not necessery for me now, but it is easy to find them I want that two.
Of course, I do not want to plot like:
    plot(X,Bex,'bo-',X,Bth,'r^-');
because the two produced lines are not smooth.
THank you in advance.

Best Answer

Add this code to the end of your script:
% Fit the Bex points
coeffs1 = polyfit(X, Bex, 2);
newX = linspace(X(1), X(end), 100);
fittedValues = polyval(coeffs1, newX);
hold on;
plot(newX, fittedValues, 'b-');
% Fit the Bth points
coeffs2 = polyfit(X, Bth, 2);
newX2 = linspace(X(1), X(end), 100);
fittedValues2 = polyval(coeffs2, newX2);
hold on;
plot(newX2, fittedValues2, 'r-');
This will fit a quadratic to your data points. You can use another order if you want. Do you know what model you want? If you don't want a polynomial, you'll have to use a different function. Look up fitting in the help. There is also a Curve Fitting Toolbox that you may have that could help.
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