pif: Pipe friendly conditional operation

In moodymudskipper/mmpipe: pipe operators and related functions

Description

Apply a transformation on the data only if a condition is met, by default if condition is not met the input is returned unchanged.

Usage

pif(x, p, true, false = identity)

Arguments

x	An object
p	A predicate function, a formula describing such a predicate function, or an expression.
true, false	Functions to apply to the data, formulas describing such functions, or expressions.

Details

The use of formula or functions is recommended over the use of expressions for the following reasons :

• If true and/or false are provided as expressions they will be evaluated wether the condition is TRUE or FALSE. Functions or formulas on the other hand will be applied on the data only if the relevant condition is met

• Formulas support calling directly a column of the data by its name without x$foo notation.

• Dot notation will work in expressions only if 'pif' is used in a pipe chain

Value

The output of true or false, either as expressions or applied on data as functions

Examples

# using functions
iris %>% pif(is.data.frame, dim, nrow)
# using formulas
iris %>% pif(~is.numeric(Species), ~"numeric :)",~paste(class(Species)[1],":("))
# using expressions
iris %>% pif(nrow(.) > 2, head(.,2))
# careful with expressions
iris %>% pif(TRUE, dim,  warning("this will be evaluated"))
 iris %>% pif(TRUE, dim, ~warning("this won't be evaluated"))

moodymudskipper/mmpipe documentation built on May 17, 2019, 10:39 a.m.