R: Recode and replace values

vec-recode-and-replace {vctrs}

R Documentation

Recode and replace values

Description

vec_recode_values() constructs an entirely new vector by recoding the values from x specified in from to the corresponding values in to. If there are values in x not matched by from, then they are recoded to the default value.
vec_replace_values() updates an existing vector by replacing the values from x specified in from with the corresponding values in to. In this case, to must have the same type as x and values in x not matched by from pass through untouched.

Usage

vec_recode_values(
  x,
  ...,
  from,
  to,
  default = NULL,
  unmatched = "default",
  from_as_list_of_vectors = FALSE,
  to_as_list_of_vectors = FALSE,
  ptype = NULL,
  x_arg = "x",
  from_arg = "from",
  to_arg = "to",
  default_arg = "default",
  error_call = current_env()
)

vec_replace_values(
  x,
  ...,
  from,
  to,
  from_as_list_of_vectors = FALSE,
  to_as_list_of_vectors = FALSE,
  x_arg = "x",
  from_arg = "from",
  to_arg = "to",
  error_call = current_env()
)

Arguments

x

A vector.

...

These dots are for future extensions and must be empty.

from

Values to locate in x and map to values in to.

Extra values present in from but not in x are ignored.

If from_as_list_of_vectors = FALSE, from must be a single vector of any size, which will be cast to the type of x.
If from_as_list_of_vectors = TRUE, from must be a list of vectors of any size, which will individually be cast to the type of x.

to

Values to map from to.

The common type of to and default will determine the type of the output, unless ptype is provided.

If to_as_list_of_vectors = FALSE, to must be a single vector of size 1 or the same size as from.
If to_as_list_of_vectors = TRUE, to must be a list of vectors. The list itself must be size 1 or the same size as from. Each individual vector in the list must be size 1 or the same size as x.

default

Default value to use when there is a value present in x that is unmatched by a value in from.

By default, a missing value is used as the default value.

If supplied, default must be size 1 or the same size as x.

Can only be set when unmatched = "default".

unmatched

Handling of unmatched locations.

One of:

"default" to use default in unmatched locations.
"error" to error when there are unmatched locations.

from_as_list_of_vectors, to_as_list_of_vectors

Boolean values determining whether to treat from and to as vectors or as lists of vectors. See their parameter descriptions for more details.

ptype

An optional override for the output type, which is usually computed as the common type of to and default.

x_arg, from_arg, to_arg, default_arg

Argument names used in error messages.

error_call

The execution environment of a currently running function, e.g. caller_env(). The function will be mentioned in error messages as the source of the error. See the call argument of abort() for more information.

Value

A vector the same size as x.

For vec_recode_values(), the type of the output is computed as the common type of to and default, unless overridden by ptype. The names of the output come from the names of to and default.
For vec_replace_values(), the type of the output will have the same type as x. The names of the output will be the same as the names of x.

Examples

x <- c(1, 2, 3, 1, 2, 4, NA, 5)

# Imagine you have a pre-existing lookup table
likert <- data.frame(
  from = c(1, 2, 3, 4, 5),
  to = c(
    "Strongly disagree",
    "Disagree",
    "Neutral",
    "Agree",
    "Strongly agree"
  )
)
vec_recode_values(x, from = likert$from, to = likert$to)

# If you don't map all of the values, a `default` is used
x <- c(1, 2, 3, 1, 2, 4, NA, 5, 6, 7)
vec_recode_values(x, from = likert$from, to = likert$to)
vec_recode_values(x, from = likert$from, to = likert$to, default = "Unknown")

# If you want existing `NA`s to pass through, include a mapping for `NA` in
# your lookup table
likert <- data.frame(
  from = c(1, 2, 3, 4, 5, NA),
  to = c(
    "Strongly disagree",
    "Disagree",
    "Neutral",
    "Agree",
    "Strongly agree",
    NA
  )
)
vec_recode_values(x, from = likert$from, to = likert$to, default = "Unknown")

# If you believe you've captured all of the cases, you can assert this with
# `unmatched = "error"`, which will error if you've missed any cases
# (including `NA`, which must be explicitly handled)
try(vec_recode_values(
  x,
  from = likert$from,
  to = likert$to,
  unmatched = "error"
))

if (require("tibble")) {
  # If you want to partially update `x`, retaining the type of `x` and
  # leaving values not covered by `from` alone, use `vec_replace_values()`
  universities <- c(
    "Duke",
    "Fake U",
    "Duke U",
    NA,
    "Chapel Hill",
    "UNC",
    NA,
    "Duke"
  )

  standardize <- tibble::tribble(
    ~from, ~to,
    "Duke", "Duke University",
    "Duke U", "Duke University",
    "UNC", "UNC Chapel Hill",
    "Chapel Hill", "UNC Chapel Hill",
  )
  vec_replace_values(
    universities,
    from = standardize$from,
    to = standardize$to
  )

  # In this case, you can use a more powerful feature of
  # `vec_replace_values()`, `from_as_list_of_vectors`, which allows you to
  # provide a list of `from` vectors that each match multiple `from` values
  # to a single `to` value. `tribble()` can help you create these!
  standardize <- tibble::tribble(
    ~from, ~to,
    c("Duke", "Duke U"), "Duke University",
    c("UNC", "Chapel Hill"), "UNC Chapel Hill",
  )

  # Note how `from` is a list column
  standardize

  vec_replace_values(
    universities,
    from = standardize$from,
    to = standardize$to,
    from_as_list_of_vectors = TRUE
  )

  # `vec_replace_values()` is also a useful way to map from or to `NA`
  vec_replace_values(universities, from = NA, to = "Unknown")
  vec_replace_values(universities, from = "Fake U", to = NA)
}

[Package vctrs version 0.7.3 Index]