Coerce polynom or polylist objects to function.

Description

Since polynom objects are represented as functions, as.function.polynom simply removes the class attribute. The function as.function.polylist produces allows all polynomials on the list to be evaluated simultaneously at the same argument value.

Usage

## S3 method for class 'polynom'
as.function(x, variable = "x", ...)
## S3 method for class 'polylist'
as.function(x, ...)

Arguments

Details

Since polynom objects are already stored as functions, as.function.polynom is rarely needed and may be replaced by unclass. An explicit call to as.function.polynom, however, will generate a slightly faster version of the function as an unrooled loop, and does allow the user to specify a different name for the formal argument to be used.

Since arithmetic on polynomials is provided, both of these functions may be evaluated at a polynom object as well as a numeric argument.

Value

An R function implementing the evaluation.

Author(s)

Bill Venables

References

None

Examples

x <- polynom()
H <- polylist(polynom(1), x)
for(j in 2:5)
    H[[j+1]] <- x*H[[j]] - (j-1)*H[[j-1]]
H5 <- as.function(H)
H5(-4:4)
H5(x+1)

Results

R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

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Type 'license()' or 'licence()' for distribution details.

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Type 'demo()' for some demos, 'help()' for on-line help, or
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Type 'q()' to quit R.

> library(PolynomF)
> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/PolynomF/as.function.polynom.Rd_%03d_medium.png", width=480, height=480)
> ### Name: as.function.polynom
> ### Title: Coerce polynom or polylist objects to function.
> ### Aliases: as.function.polynom as.function.polylist
> ### Keywords: symbolmath
> 
> ### ** Examples
> 
> x <- polynom()
> H <- polylist(polynom(1), x)
> for(j in 2:5)
+     H[[j+1]] <- x*H[[j]] - (j-1)*H[[j-1]]
> H5 <- as.function(H)
> H5(-4:4)
      [,1] [,2] [,3] [,4] [,5] [,6]
 [1,]    1   -4   15  -52  163 -444
 [2,]    1   -3    8  -18   30  -18
 [3,]    1   -2    3   -2   -5   18
 [4,]    1   -1    0    2   -2   -6
 [5,]    1    0   -1    0    3    0
 [6,]    1    1    0   -2   -2    6
 [7,]    1    2    3    2   -5  -18
 [8,]    1    3    8   18   30   18
 [9,]    1    4   15   52  163  444
> H5(x+1)
[[1]]
1 

[[2]]
1 + x 

[[3]]
2*x + x^2 

[[4]]
-2 + 3*x^2 + x^3 

[[5]]
-2 - 8*x + 4*x^3 + x^4 

[[6]]
6 - 10*x - 20*x^2 + 5*x^4 + x^5 

> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>