poly.calc: Calculate Polynomials from Zeros or Values

In polynom: A Collection of Functions to Implement a Class for Univariate Polynomial Manipulations

Calculate Polynomials from Zeros or Values

Description

Calculate either the monic polynomial with specified zeros, or the Lagrange interpolation polynomial through the (x,y) points.

Usage

poly.calc(x, y, tol=sqrt(.Machine$double.eps), lab=dimnames(y)[[2]])

Arguments

x	numeric vector specifying either the zeros of the desired polynomial if this is the only non-missing argument, or the x-values for Lagrange interpolation.
y	numeric vector or matrix specifying the y-values for the Lagrange interpolation polynomial. If y is a matrix, nrow(y) must equal length(x), and each column of y is used separately with x.
tol	An absolute value tolerance, below which coefficients are treated as zero.
lab	If y is a matrix, lab is used as the names vector for the list result.

Details

If y is a matrix, the result is a list of polynomials using each column separately.

If x only is given, repeated zeros are allowed. If x and y are given, repeated values in the x vector must have identical y values associated with them (up to tol), otherwise the first y-value only is used and a warning is issued.

Value

Either a polynomial object, or a list of polynomials, as appropriate. In the latter case the object is of class "polylist".

See Also

polynomial

Examples

poly.calc(rep(1,3))
## -1 + 3*x - 3*x^2 + x^3 
poly.calc(0:4, (0:4)^2 + 1)
## 1 + x^2 
poly.calc(0:4, cbind(0:4, (0:4)^2 + 1), lab = letters[1:2])
## List of polynomials:
## $a:
## x
##
## $b:
## 1 + x^2 

polynom documentation built on April 11, 2022, 9:05 a.m.