Change a multivariate polynomial into a function.

Transforms an mpoly object into a function which can be evaluated.

# S3 method for mpoly
as.function(x, varorder = vars(x), vector = TRUE,
  silent = FALSE, ..., plus_pad = 1L, times_pad = 1L, squeeze = TRUE)

Arguments

x	an object of class mpoly
varorder	the order of the variables
vector	whether the function should take a vector argument (TRUE) or a series of arguments (FALSE)
silent	logical; if TRUE, suppresses output
...	any additional arguments
plus_pad	number of spaces to the left and right of plus sign
times_pad	number of spaces to the left and right of times sign
squeeze	minify code in the created function

See also

plug(), as.function.mpolyList()

Examples

p <- mp("(x - 1)^2")
(f <- as.function(p))
#> f(.) with . = x
#> function (.) 
#> {
#>     if (length(.) > 1) {
#>         .[] <- sapply(., f)
#>         return(.)
#>     }
#>     .^2 - 2 * . + 1
#> }
#> <environment: 0x7fae3e919a10>
f(1)
#> [1] 0
f(seq(0, 2, .1))
#>  [1] 1.00 0.81 0.64 0.49 0.36 0.25 0.16 0.09 0.04 0.01 0.00 0.01 0.04 0.09 0.16
#> [16] 0.25 0.36 0.49 0.64 0.81 1.00

p <- mp("x + 3 x y + z^2 x")
(f <- as.function(p))
#> f(.) with . = (x, y, z)
#> function (.) 
#> {
#>     .[1] + 3 * .[1] * .[2] + .[1] * .[3]^2
#> }
#> <environment: 0x7fae3d8fc040>
f(1:3) # -> 16
#> [1] 16
f(c(1,1,1)) # -> 5
#> [1] 5

f <- as.function(p, vector = FALSE)
#> f(x, y, z)
f(1, 2, 3) # -> 16
#> [1] 16
f(1, 1, 1) # -> 5
#> [1] 5

f <- as.function(p, varorder = c("z","y","x"), vector = FALSE)
#> f(z, y, x)
f(3, 2, 1) # -> 16
#> [1] 16
f(1, 1, 1) # -> 5
#> [1] 5

# for univariate mpolys, as.function() returns a vectorized function
# that can even apply to arrays
p <- mp("x^2")
f <- as.function(p)
#> f(.) with . = x
f(1:10)
#>  [1]   1   4   9  16  25  36  49  64  81 100
(mat <- matrix(1:4, 2))
#>      [,1] [,2]
#> [1,]    1    3
#> [2,]    2    4
f(mat)
#>      [,1] [,2]
#> [1,]    1    9
#> [2,]    4   16


p <- mp("1 2 3 4")
f <- as.function(p)
f(10) # -> 24
#> [1] 24

bernstein(1, 2)
#> 2 x  -  2 x^2
s <- seq(0, 1, .01)
as.function(bernstein(1, 2))(s)
#> f(.) with . = x
#>   [1] 0.0000 0.0198 0.0392 0.0582 0.0768 0.0950 0.1128 0.1302 0.1472 0.1638
#>  [11] 0.1800 0.1958 0.2112 0.2262 0.2408 0.2550 0.2688 0.2822 0.2952 0.3078
#>  [21] 0.3200 0.3318 0.3432 0.3542 0.3648 0.3750 0.3848 0.3942 0.4032 0.4118
#>  [31] 0.4200 0.4278 0.4352 0.4422 0.4488 0.4550 0.4608 0.4662 0.4712 0.4758
#>  [41] 0.4800 0.4838 0.4872 0.4902 0.4928 0.4950 0.4968 0.4982 0.4992 0.4998
#>  [51] 0.5000 0.4998 0.4992 0.4982 0.4968 0.4950 0.4928 0.4902 0.4872 0.4838
#>  [61] 0.4800 0.4758 0.4712 0.4662 0.4608 0.4550 0.4488 0.4422 0.4352 0.4278
#>  [71] 0.4200 0.4118 0.4032 0.3942 0.3848 0.3750 0.3648 0.3542 0.3432 0.3318
#>  [81] 0.3200 0.3078 0.2952 0.2822 0.2688 0.2550 0.2408 0.2262 0.2112 0.1958
#>  [91] 0.1800 0.1638 0.1472 0.1302 0.1128 0.0950 0.0768 0.0582 0.0392 0.0198
#> [101] 0.0000
plot(
  s,
  as.function(bernstein(1, 2))(s)
)
#> f(.) with . = x


as.function(mp("x + xx"))
#> f(.) with . = (x, xx)
#> function (.) 
#> {
#>     .[1] + .[2]
#> }
#> <environment: 0x7fae3f531830>
as.function(mp("x + xx"), squeeze = FALSE)
#> f(.) with . = (x, xx)
#> function (.) 
#> {
#>     .[1] + .[2]
#> }
#> <environment: 0x7fae3e41d5e8>