interpolation - R-help | R Mailing Lists

Mon, Nov 4, 2002 5:32 AM #

Hello Marwan:

Marwan Khawaja wrote:

Are you trying to extrapolate?

It depends of many things...
Are you fitting a particular model?
Is the linear model enough?

Kenneth Roy Cabrera Torres
Celular +57 (315) 405 9339



-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

Douglas Bates

Mon, Nov 4, 2002 8:38 AM #

"Marwan Khawaja" <mk36 at aub.edu.lb> writes:

I'm not sure if I understand what you are asking.  The phrase "back in
time" seems to indicate extrapolation rather than interpolation.

You could try interpSpline in the splines package.  That produces a
"natural spline" that can be used for interpolation within the range
of the data or extrapolation beyond the range of the data.  Linear
extrapolation, based on the derivative of the fitted function at the
end points, is used.
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

Marwan Khawaja

Mon, Nov 4, 2002 1:33 PM #

Hello,
I have 15 data points (weight at birth) by age which I want to interpolate back
in time (to 5 more age points).
There are many functions in R to do this and I wonder if anyone has experience
in using these -- any preference/caveat etc? I am trying to find an alternative
to linear interpolation.
Using R 1.6.0 under windows
TIA Marwan

--------------------------------------------------------------------------------
--------------------------------------------------------
Marwan Khawaja   -   http://webfaculty.aub.edu.lb/~mk36/     If you have MS
Internet Explorer!
--------------------------------------------------------------------------------
--------------------------------------------------------

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._