fitting a scatter plot to power law

I have an array A(5,2). how can i fit it to a power law y= c1*x^n1+c2*x^n2 in wich C1, C2, n1 and n2 are real numbers and yet to be determined from the fit?

Thank you

Answer 1

[Star Strider]

One approach:

objfcn = @(b,x) b(1).*x.^b(3) + b(2).*x.^b(4);

x = 1:10;                                                                   % Create Data
y = rand(1, 10);                                                            % Create Data

B0 = ones(4,1);
[B,rsdnrm] = fminsearch(@(b) norm(y - objfcn(b,x)), B0);
fprintf(1, 'c_1 = %12.6f\nc_2 = %12.6f\nn_1 = %12.6f\nn_2 = %12.6f\n', B)

Experiment to get the result you want.

EDIT — (24 Sep 2019 at 15:19)

I have no idea how ‘A’ fits into this, since it was not described in any detail.

A guess:

[B,rsdnrm] = fminsearch(@(b) norm(A(:,2) - objfcn(b,A(:,1))), B0);

This fits the second column of ‘A’ to the first column, using the function. Reverse the column designations if necessary.