[R] returns the value of a polynomial of degree n evaluated a t x.

Liaw, Andy andy_liaw at merck.com
Mon Aug 9 05:27:38 CEST 2004


Try something like:

install.packages("polynom")
library(polynom)
predict(polynomial(rev(p)), x)

HTH,
Andy

> From: McClatchie, Sam (PIRSA-SARDI)
> 
> > Background:
> > OS: Linux Mandrake 9.1
> > release: R 1.9.0 
> > editor: Xemacs 21.4
> > frontend: ESS 5.1.23
> > ---------------------------------
> > 
> > Colleagues
> > 
> Is there a function in R that is similar to polyval in matlab? (y =
> polyval(p,x) returns the value of a polynomial of degree n 
> evaluated at x.
> The input argument p is a vector of length n+1 whose elements are the
> coefficients in descending powers of the polynomial to be evaluated).
> <http://www.mathworks.com/access/helpdesk/help/techdoc/ref/pol
yval.html> 
 
I have possibly missed it in the R help files, so please excuse me if I
have. "Polynomial evaluation" yielded no result in a search of help, and the
functions poly() and locpoly() don't seem to be what I am after.

> Sam
> ----
> Sam McClatchie,
> Sub-program leader, Pelagic Fisheries
> South Australian Aquatic Sciences Centre
> PO Box 120, Henley Beach 5022
> Adelaide, South Australia
> email <mcclatchie.sam at saugov.sa.gov.au>
> Telephone: (61-8) 8200 2448
> FAX: (61-8) 8200 2481
> Research home page <http://www.smcc.150m.com/>
>   
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