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How can I create a best fit polynomial for my data?

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Syed Ali Zaryab
Syed Ali Zaryab el 4 de Sept. de 2018
Comentada: Titus Edelhofer el 9 de Sept. de 2018
I have a set of data points that I received from a supplier which gives relative efficiency based on values of x and y. I want to create a polynomial similar to the one given below using the data provided Efficiency = a * (x)^2 + b * (x*y) + c * (y)^2 + d * (x)+ e * (y) + f
So basically what I want is a function which optimizes the value of a,b,c,d,e and f for me and gives me results that are almost similar to the one in the data table.
Attached herewith is the picture of the graph that the supplier provided along with the data points. Can you please tell me what functions can I use in Matlab to help me achieve this task.

Respuesta aceptada

Titus Edelhofer
Titus Edelhofer el 4 de Sept. de 2018
Hi Syed,
if I assume you have three (column) vectors x, y and Efficiency, then it's simply a linear regression problem:
A = [x.^2 x.*y y.^2 x y ones(size(x))];
sol = A \ Efficiency;
Then sol contains the (best approximation) values a,...,f.
Titus
  3 comentarios
Torsten
Torsten el 7 de Sept. de 2018
Use "reshape" to change x, eff and y from (4x13) matrices to (52x1) vectors.
Titus Edelhofer
Titus Edelhofer el 9 de Sept. de 2018
Or use (:), i.e.,
x = x(:);
y = y(:);
eff = eff(:);
Titus

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