vec-set {vctrs}

Set operations

Description

• vec_set_intersect() returns all values in both x and y.

• vec_set_difference() returns all values in x but not y. Note that this is an asymmetric set difference, meaning it is not commutative.

• vec_set_union() returns all values in either x or y.

• vec_set_symmetric_difference() returns all values in either x or y but not both. This is a commutative difference.

Because these are set operations, these functions only return unique values from x and y, returned in the order they first appeared in the original input. Names of x and y are retained on the result, but names are always taken from x if the value appears in both inputs.

These functions work similarly to intersect(), setdiff(), and union(), but don't strip attributes and can be used with data frames.

Usage

vec_set_intersect(
  x,
  y,
  ...,
  ptype = NULL,
  x_arg = "x",
  y_arg = "y",
  error_call = current_env()
)

vec_set_difference(
  x,
  y,
  ...,
  ptype = NULL,
  x_arg = "x",
  y_arg = "y",
  error_call = current_env()
)

vec_set_union(
  x,
  y,
  ...,
  ptype = NULL,
  x_arg = "x",
  y_arg = "y",
  error_call = current_env()
)

vec_set_symmetric_difference(
  x,
  y,
  ...,
  ptype = NULL,
  x_arg = "x",
  y_arg = "y",
  error_call = current_env()
)

Arguments

x, y

A pair of vectors.

...

These dots are for future extensions and must be empty.

ptype

If NULL, the default, the output type is determined by computing the common type between x and y. If supplied, both x and y will be cast to this type.

x_arg, y_arg

Argument names for x and y. These are 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.

Details

Missing values are treated as equal to other missing values. For doubles and complexes, NaN are equal to other NaN, but not to NA.

Value

A vector of the common type of x and y (or ptype, if supplied) containing the result of the corresponding set function.

Dependencies

vec_set_intersect()

• vec_proxy_equal()

• vec_slice()

• vec_ptype2()

• vec_cast()

vec_set_difference()

• vec_proxy_equal()

• vec_slice()

• vec_ptype2()

• vec_cast()

vec_set_union()

• vec_proxy_equal()

• vec_slice()

• vec_ptype2()

• vec_cast()

• vec_c()

vec_set_symmetric_difference()

• vec_proxy_equal()

• vec_slice()

• vec_ptype2()

• vec_cast()

• vec_c()

Examples

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

# All unique values in both `x` and `y`.
# Duplicates in `x` and `y` are always removed.
vec_set_intersect(x, y)

# All unique values in `x` but not `y`
vec_set_difference(x, y)

# All unique values in either `x` or `y`
vec_set_union(x, y)

# All unique values in either `x` or `y` but not both
vec_set_symmetric_difference(x, y)

# These functions can also be used with data frames
x <- data_frame(
  a = c(2, 3, 2, 2),
  b = c("j", "k", "j", "l")
)
y <- data_frame(
  a = c(1, 2, 2, 2, 3),
  b = c("j", "l", "j", "l", "j")
)

vec_set_intersect(x, y)
vec_set_difference(x, y)
vec_set_union(x, y)
vec_set_symmetric_difference(x, y)

# Vector names don't affect set membership, but if you'd like to force
# them to, you can transform the vector into a two column data frame
x <- c(a = 1, b = 2, c = 2, d = 3)
y <- c(c = 2, b = 1, a = 3, d = 3)

vec_set_intersect(x, y)

x <- data_frame(name = names(x), value = unname(x))
y <- data_frame(name = names(y), value = unname(y))

vec_set_intersect(x, y)