Interpolating with f(x) = a*x^b, where b might be a non-integer?

[Joanna Rutkowska]

Hello, given a set of measurements, I would like to find the best 
fitting function of the form:

f(x) = a*x^b, where a, b might be non integers. Here is a good example 
of such a fitting:

http://www.flybrushless.com/prop/view/38

Is there any toolbox in octave that I could use to easily obtain the a 
and b coefficients given a set of measurements?

Thanks,
joanna.