Fit a curve of equation of form y = ax^b to data

Hi,

How do I fit a curve of equation of form y = ax^b to my data. I have x and y values. I have to find a and b (it can be a fraction) and plot the curve.

[Sussana Okeleye]

Hi , did you ever figure out how to do this?

Answer 1

[Honglei Chen]

If you have Curve Fitting Toolbox, you can use that to do an exponential fitting directly

http://www.mathworks.com/help/toolbox/curvefit/bszh0sy-5.html

If not, you can take logarithm of both sides and translate that into a linear fitting problem, i.e.

log(y) = log(a)+b*log(x)

and then use polyfit

http://www.mathworks.com/help/techdoc/ref/polyfit.html

Answer 2

[Sean de Wolski]

Any of these are designed for this.

• lsqcurvefit Optimization Toolbox
• nlinfit Statistics Toolbox
• NonlinearModel Statistics Toolbox >= R2012a.

Answer 3

[hitesh Mehta]

Hi,

How do I fit a curve of equation of form y = ax^b+c to my data. I have x and y and c values.

I have to find a and b(it can be a fraction) and plot the curve.