# [R] interpolation and numerical differentiation in R ?

Robert D. Merithew merithew at ccmr.cornell.edu
Sat Sep 1 22:53:41 CEST 2001

```Hi,

I'm trying to determine if R is useful to me.  I've browsed 'The Basics of
S and S-Plus' (Krause & Olson), and like the logic of the language.
However, I don't see an easy way to do things like this:

* given a set of observations (x,y) (x and y equal-length vectors), and a
2nd set of abscissas x2, interpolate y at the new abscissas x2.  (for now,
I don't really care what kind of interpolation -- linear, some type of
spline, etc.)

* given observations (x,y), (with unequally-spaced x), create vector z
with the numerical derivative of y with respect to x (eg evaluated at the
values x).

I'm sure I could loop over the observations and do the interpolation and
differentiation point-by-point, but that kind of defeats the purpose of a
'vectorized' environment, I think.

I analyze data from solid-state physics experiments, and very little of
the analysis is really *statistical*, so it may be that R is the wrong
tool for me.

If anyone can point me toward documentation covering how to do tasks like
the above in R, I'd appreciate it.

thanks,

-Robert Merithew, PhD			rdm28 at cornell.edu
LASSP, Cornell University
Ithaca, NY

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