translation of the matlab PPVAL function

Hello,

I am trying to translate a matlab program into R, and I have some problems
to find out how to translate the PPVAL function.
I know that ppval(pp,xx) returns the value at the points xx of the
piecewise polynomial contained in pp( constructed by spline), but I don't
know how to do the same thing in R.

Thanks for you help


Delphine