Extraction analytical eqution from interpolant fitting?

How can i extract analytical equation from cfit, when i use interpolant fitting (e.g. cubic spline)?

Answer 1

[Walter Roberson]

When you asked this question about a day ago, you wrote in terms of "symbolic" expression rather than analytical expression.

To answer your question you are going to need to describe the form of analytical equation you need. cubic splines are inherently defined piece-wise, so there is not going to be a single equation unless you start using piecewise() or heaviside() or similar.

You should have a look at http://www.mathworks.com/help/matlab/ref/unmkpp.html

[Izya Catsman]

Yeah, thank you, your link has been most helpful. I solved my problem using spline() and ppval() commands. I still dont uderstand why you can't just get the equation stright from the curve fitting application, for instance: ppval(SomeOperator(cfit),xx). May be it cuz i'm noob) But it doesn't matter now.

PS: Sorry for spamming this question, i was desperate for help, and site returned some wierd error every time i sent it)