function_to_pmml {pmml}

Convert an R expression to PMML.

Description

Convert an R expression to PMML.

Usage

function_to_pmml(expr)

Arguments

expr

An R expression enclosed in quotes.

Details

As long as the expression passed to the function is a valid R expression (e.g., no unbalanced parenthesis), it can contain arbitrary function names not defined in R. Variables in the expression passed to 'xform_function' are always assumed to be fields, and not substituted. That is, even if 'x' has a value in the R environment, the resulting expression will still use 'x'.

An expression such as 'foo(x)' is treated as a function 'foo' with argument 'x'. Consequently, passing in an R vector 'c(1,2,3)' to 'function_to_pmml()' will produce PMML where 'c' is a function and '1,2,3' are the arguments.

An expression starting with '-' or '+' (for example, "-3" or "-(a+b)") will be treated as if there is a 0 before the initial '-' or '+' sign. This makes it possible to represent expressions that start with a sign, since PMML's '-' and '+' functions require two arguments. The resulting PMML node will have a constant 0 as a child.

Value

PMML version of the input expression

Author(s)

Dmitriy Bolotov

Examples

# Operator precedence and parenthesis
func_pmml <- function_to_pmml("1 + 3/5 - (4 * 2)")

# Nested arbitrary functions
func_pmml <- function_to_pmml("foo(bar(x)) - bar(foo(y-z))")

# If-else expression
func_pmml <- function_to_pmml("if (x==3) { 3 } else { 0 }")

# If-else with boolean output
func_pmml <- function_to_pmml("if (x==3) { TRUE } else { FALSE }")

# Function with string argument types
func_pmml <- function_to_pmml("colors('red','green','blue')")

# Sign in front of expression
func_pmml <- function_to_pmml("-(x/y)")