MATLAB: How to match curve with equations

matlab function

Is there a simple way for Matlab to keep testing coefficients of the two equations in the red box such that the above curve is produced?

(I have another known function that produces the curve)

Best Answer

There is. MATLAB has several functions and one Toolbox devoted to solving that problem, called parameter estimation.

See specifically the Statistics Toolbox nlinfit, the Optimization Toolbox lsqcurvefit, the core MATLAB function fminsearch functions, and the Curve Fitting Toolbox for details.

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MATLAB: How to fit inverse proportional function

Your function could be difficult to fit. You can use the fminsearch function to estimate the parameters:

% Define ‘x’ and ‘y’ here
% Parameter Vector: b(1) = a,  b(2) = b,  b(3) = c
yfit = @(b,x) b(1)./(x + b(2)) + b(3);  % Objective Function
CF = @(b) sum((y-yfit(b,x)).^2);        % Cost Function
b0 = rand(1,3)*10;                      % Initial Parameter Estimates
[B, fv] = fminsearch(CF, b0);           % Estimate Parameters

Note that ‘x’ and ‘y’ have to be defined in your workspace

MATLAB: Plot function of 3 variables

Three variables plus one result = 4 dimensions. To represent the 4th dimension you will need to use color or transparency or shading or marker size or marker shape.

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MATLAB: How to fit inverse proportional function

MATLAB: Plot function of 3 variables

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