R: Coerce a Polynomial to a Function

as.function.polynomial {polynom} | R Documentation

## Coerce a Polynomial to a Function

### Description

Takes a polynomial argument and constructs an R function to evaluate it at arbitrary points.

### Usage

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

### Arguments

`x` | An object of class `"polynomial"`.
`...` | further arguments to be passed to or from methods.

### Details

This is a method for the generic function `as.function`.

The polynomial is evaluated within the function using the Horner scheme.

Note that you can use the model-oriented `predict` method for polynomials for purpose of evaluation (without explicit coercion to a function), see the example below.

### Value

A function to evaluate the polynomial `p`.

### See Also

`as.function`, `predict.polynomial`

### Examples

    pr <- (poly.calc(-1:1) - 2 * polynomial(c(1, 2, 1)))^2
    pr
    ## 4 + 20*x + 33*x^2 + 16*x^3 - 6*x^4 - 4*x^5 + x^6
    prf <- as.function(pr)
    prf
    ## function (x)
    ## 4 + x * (20 + x * (33 + x * (16 + x * (-6 + x * (-4 + x * (1))))))
    ## <environment: 0x402440f0>
    prf(-3:3)
    ##  1024 64  0 4 64 144 64
    predict(pr, -3:3)
    ##  1024 64  0 4 64 144 64

[Package polynom version 1.3-9 Index]