Fit in matlab equations

How can I fir cube equation in matlab

Answer 1

[Daniel Pereira]

Did you try

z = x^-3;
p = polyfit(z,y,1)

then

yy = p(1) * z + p(2);

which has the form

yy = a * x.^-3 + b;

[Ede gerlderlands]

I modified my question as per your suggestion. There are issues I mentioned in the questions. Thank you