[SciPy-User] help interpreting univariate spline

[David Warde-Farley]

On 2010-04-30, at 4:14 PM, Elliot Hallmark wrote:

> um, I think this is what I already have done?  But the "semi standard"
> spline representation in tck is completely undocumented as far as I
> can tell.  The only way to get the polynomial coefficents I can tell
> is through evaluating the derivatives.

It's documented, in the FITPACK user's manual, and possibly in that book that I pointed you to in another reply.

> Do you know what is the meaning of the coefficents splrep generates?
> How could such a small set of coefficents represent all the
> information of a cubic function?

Probably because they are not general cubic functions. They are constrained to have equal 0th through 2nd derivatives at each of the knot points. This limits the degrees of freedom considerably.

David