Nested if else

nif is a fast implementation of SQL CASE WHEN statement for R. Conceptually, nif is a nested version of iif (with smarter implementation than manual nesting). It is not the same but it is comparable to dplyr::case_when and data.table::fcase.

Usage

nif(..., default=NULL)

Arguments

...: A sequence consisting of logical condition (when)-resulting value (value) pairs in the following order when1, value1, when2, value2, ..., whenN, valueN. Logical conditions when1, when2, ..., whenN must all have the same length, type and attributes. Each value may either share length with when or be length 1. Please see Examples section for further details.
default: Default return value, NULL by default, for when all of the logical conditions when1, when2, ..., whenN are FALSE or missing for some entries. Argument default can be a vector either of length 1 or length of logical conditions when1, when2, ..., whenN. Note that argument 'default' must be named explicitly.

Value

Vector with the same length as the logical conditions (when) in ..., filled with the corresponding values (value) from ..., or eventually default. Attributes of output values value1, value2, ...valueN in ... are preserved.

Details

Unlike data.table::fcase, the default argument is set to NULL. In addition, nif can be called by other packages at C level. Note that at C level, the function has an additional argument SEXP md which is either TRUE for lazy evaluation or FALSE for non lazy evaluation. This argument is not exposed to R users and is more for C users.

Author

Morgan Jacob

Examples

x = 1:10
nif(
  x < 5L, 1L,
  x > 5L, 3L
)
#>  [1]  1  1  1  1 NA  3  3  3  3  3

nif(
  x < 5L, 1L:10L,
  x > 5L, 3L:12L
)
#>  [1]  1  2  3  4 NA  8  9 10 11 12

# Lazy evaluation example
nif(
  x < 5L, 1L,
  x >= 5L, 3L,
  x == 5L, stop("provided value is an unexpected one!")
)
#>  [1] 1 1 1 1 3 3 3 3 3 3

# nif preserves attributes, example with dates
nif(
  x < 5L, as.Date("2019-10-11"),
  x > 5L, as.Date("2019-10-14")
)
#>  [1] "2019-10-11" "2019-10-11" "2019-10-11" "2019-10-11" NA          
#>  [6] "2019-10-14" "2019-10-14" "2019-10-14" "2019-10-14" "2019-10-14"

# nif example with factor; note the matching levels
nif(
  x < 5L, factor("a", levels=letters[1:3]),
  x > 5L, factor("b", levels=letters[1:3])
)
#>  [1] a    a    a    a    <NA> b    b    b    b    b   
#> Levels: a b c

# Example of using the 'default' argument
nif(
  x < 5L, 1L,
  x > 5L, 3L,
  default = 5L
)
#>  [1] 1 1 1 1 5 3 3 3 3 3

nif(
  x < 5L, 1L,
  x > 5L, 3L,
  default = rep(5L, 10L)
)
#>  [1] 1 1 1 1 5 3 3 3 3 3