Online polynomial linear curve fitting in Simulink
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How to fit curves in Simulink and still generate the code?
I have a model of a sensor in Simulink, that returns vectors "Pos_x" and "Pos_y". Each vector has size of 20x1, whose values change every one step time (1ms).
I am trying to calculate the coeffecients of the 3rd degree Polynomial y(x) = p1*x^3 + p2*x^2 + p3*x + p4 in Simulink, that fits the data.
I did not find any block in simulink that calculates the coeffecients, so I used a simple Matlab function
function [p1, p2, p3, p4] = fcn(x,y)
% f(x) = p1*x^3 + p2*x^2 + p3*x + p4
f = fit(x', y', 'Poly3'); % I have also tried "polyfit"
p1 = f.p1;
p2 = f.p2;
p3 = f.p3;
p4 = f.p4;
but I get the error: Function 'fit' not supported for code generation.
1- so back to my qustion, How to fit curves in Simulink and still generate the code?
2- I am also open to any other suggestion
Jonas on 31 Aug 2021
If you have the DSP Systems Toolbox you can use the Least Squares Polynomial Fit block.
Standard Simulink does not have an alternative as far as I can see. Unless you implement a curve fitting algorithm yourself in a MATLAB Function block. If it is just for testing some stuff the DSP Systems Toolbox seems the alternative.