gsl (version 2.1-1)

Poly: Polynomials

Description

Polynomial functions as per the Gnu Scientific Library, reference manual section 6.1. These functions are defined in header file gsl_poly.h

Usage

gsl_poly(c_gsl,x)

Arguments

c_gsl

Coefficients of the poynomial (c in the function definition and the GSL ref manual) starting at the constant term and ending in the highest power; see details section. This argument is called “c_gsl” (and not “c”) to avoid confusion with R function c()

x

input: real values

Details

One must be careful to avoid off-by-one errors. In C idiom, the function evaluates the polynomial $$c[0]+c[1]x+c[2]x^2+\ldots+c[\mathrm{len}-1]x^{\mathrm{len}-1}$$ where len is the second argument of GSL function gsl_poly_eval().

The R idiom would be $$c[1]+c[2]x+c[3]x^2+\ldots+c[\mathrm{len}]x^{\mathrm{len}-1}.$$

This section is work-in-progress and more will be added when I have the time/need for the other functions here.

References

http://www.gnu.org/software/gsl

Examples

a <- matrix(1:4,2,2)
rownames(a) <- letters[1:2]
(jj <- gsl_poly(1:3,a))

jj-(1 + 2*a + 3*a^2)  #should be small