polyfit

A follow-up to the previous post.

Polynomial fitting is also very easy with the numpy packages polyfit and poly1d.

In [196]: x = range(100)
In [197]: y = randn(100)
In [198]: plot(x,y)
Out[198]: []

Here I am asking polyfit to fit me a 2nd degree polynomial.

In [199]: polyfit(x,y,2)
Out[199]: array([-0.00018313,  0.01669275, -0.09621319])

The polyfit function returns the polynomial coefficients in a list.
If I want to use them directly as a fit function, just embed them in a new polynomial object:

In [200]: fitfunc = poly1d(polyfit(x,y,2))
In [201]: plot(x,fitfunc(x))
Out[201]: []

Saving the plot like this

In [202]: savefig('/Users/maye/Desktop/blog_polyfit.png')

and looks like this: