R: Vectorised switch

vswitch/nswitch {kit}

R Documentation

Vectorised switch

Description

vswitch/ nswitch is a vectorised version of base function switch. This function can also be seen as a particular case of function nif, as shown in examples below, and should also be faster.

Usage

    vswitch(x, values, outputs, default=NULL,
            nThread=getOption("kit.nThread"),
            checkEnc=TRUE)
    nswitch(x, ..., default=NULL,
            nThread=getOption("kit.nThread"),
            checkEnc=TRUE)

Arguments

`x`	A vector or list.
`values`	A vector or list with values from `x` to match. Note that `x` and `values` must have the same class and attributes.
`outputs`	A list or vector with the outputs to return for every matching values. Each item of the list must be of length 1 or length of `x`. Note that if all list items are of length 1 then it might be simpler to use a vector.
`...`	A sequence of values and outputs in the following order `value1, output1, value2, output2, ..., valueN, outputN`. Values `value1, value2, ..., valueN` must all have length1, same type and attributes. Each `output` may either share length with `x` or be length 1. Please see Examples section for further details.
`default`	Values to return is no match. Must be a vector or list of length 1 or same length as `x`. Also, `default` must have the same type, class and aatributes as items from `outputs`.
`nThread`	A integer for the number of threads to use with openmp. Default value is `getOption("kit.nThread")`.
`checkEnc`	A logical value whether or not to check if `x` and `values` have comparable and consistant encoding. Default is `TRUE`.

Value

A vector or list of the same length as x with values from outputs items and from default if missing.

Author(s)

Morgan Jacob

Examples

x = sample(c(10L, 20L, 30L, 40L, 50L, 60L), 3e2, replace=TRUE)

# The below example of 'vswitch' is
a1 = vswitch(
  x = x,
  values = c(10L,20L,30L,40L,50L),
  outputs = c(11L,21L,31L,41L,51L),
  default = NA_integer_
)

# equivalent to the following 'nif' example.
# However for large vectors 'vswitch' should be faster.
b1 = nif(
  x==10L, 11L,
  x==20L, 21L,
  x==30L, 31L,
  x==40L, 41L,
  x==50L, 51L,
  default = NA_integer_
)
identical(a1, b1)

# nswitch can also be used as follows:
c1 = nswitch(x,
  10L, 11L,
  20L, 21L,
  30L, 31L,
  40L, 41L,
  50L, 51L,
  default = NA_integer_
)
identical(a1, c1)

# Example with list in 'outputs' argument
y = c(1, 0, NA_real_)
a2 = vswitch(
  x = y,
  values = c(1, 0),
  outputs = list(c(2, 3, 4), c(5, 6, 7)),
  default = 8
)

b2 = nif(
  y==1, c(2, 3, 4),
  y==0, c(5, 6, 7),
  default = 8
)

identical(a2, b2)

c2 = nswitch(y,
  1, c(2, 3, 4),
  0, c(5, 6, 7),
  default = 8
)

identical(a2, c2)

# Benchmarks
# ----------
# x = sample(1:100, 3e8, TRUE) # 1.1Gb
# microbenchmark::microbenchmark(
# nif=kit::nif(
#   x==10L,  0L,
#   x==20L, 10L,
#   x==30L, 20L,
#   default= 30L
#  ),
# vswitch=kit::vswitch(
#   x, c( 10L, 20L, 30L), list(0L, 10L, 20L), 30L
# ),
# times=10L
# )
# Unit: seconds
#    expr   min    lq  mean median   uq  max neval
# nif      4.27  4.37  4.43   4.42 4.52 4.53    10
# vswitch  1.08  1.09  1.20   1.10 1.43 1.44    10 # 1 thread
# vswitch  0.46  0.57  0.57   0.58 0.58 0.60    10 # 2 threads

[Package kit version 0.0.10 Index]