as.function.spray {spray}

Coerce a spray object to a function

Description

Coerce a spray object to a function

Usage

## S3 method for class 'spray'
as.function(x,...)

Arguments

x

spray object, interpreted as a multivariate polynomial

...

Further arguments, currently ignored

Value

Returns a function; this function returns a numeric vector.

Note

Coercion is possible even if some indices are zero or negative. The function is not vectorized in the arity of its argument.

Author(s)

Robin K. S. Hankin

Examples

(S <- spray(matrix(1:6,3,2),1:3))
(f <- as.function(S))
f(2:3) == 3*2^3*3^6 + 2*2^2*3^5 + 1*2^1*3^4  # should be TRUE


S1 <- spray(matrix(sample(-2:2,replace=TRUE,21),ncol=3),rnorm(7),addrepeats=TRUE)
S2 <- spray(matrix(sample(-2:2,replace=TRUE,15),ncol=3),rnorm(5),addrepeats=TRUE)

f1 <- as.function(S1)
f2 <- as.function(S2)

f3 <- as.function(S1*S2)


x <- 4:6

f1(x)*f2(x)-f3(x)  # should be zero



# coercion is vectorized:

f1(matrix(1:33,ncol=3))