vec_ptype() finds the prototype of a single vector. vec_ptype_common() finds the common type of multiple vectors. vec_ptype_show() nicely prints the common type of any number of inputs, and is designed for interactive exploration.

vec_ptype(x)

vec_ptype_common(..., .ptype = NULL)

vec_ptype_show(...)

Arguments

..., x

Vectors inputs

.ptype

If NULL, the default, the output type is determined by computing the common type across all elements of ....

Alternatively, you can supply .ptype to give the output known type. If getOption("vctrs.no_guessing") is TRUE you must supply this value: this is a convenient way to make production code demand fixed types.

Value

vec_ptype() and vec_ptype_common() return a prototype (a size-0 vector)

Details

vec_ptype_common() first finds the prototype of each input, then successively calls vec_ptype2() to find a common type.

Prototype

A prototype is size 0 vector containing attributes, but no data. Generally, this is just vec_slice(x, 0L), but some inputs require special handling.

For example, the prototype of logical vectors that only contain missing values is the special unspecified type, which can be coerced to any other 1d type. This allows bare NAs to represent missing values for any 1d vector type.

The prototype of NULL

In general we treat NULL as an absence of argument (which is often an error). In the case of vec_ptype() and vec_ptype_common(), we have chosen NULL as the identity of the common type monoid: the common type of foo and NULL is always foo. For this reason, the prototype of NULL is NULL.

Examples

# Unknown types ------------------------------------------ vec_ptype_show()
#> Prototype: NULL
vec_ptype_show(NA)
#> Prototype: logical
vec_ptype_show(NULL)
#> Prototype: NULL
# Vectors ------------------------------------------------ vec_ptype_show(1:10)
#> Prototype: integer
vec_ptype_show(letters)
#> Prototype: character
vec_ptype_show(TRUE)
#> Prototype: logical
vec_ptype_show(Sys.Date())
#> Prototype: date
vec_ptype_show(Sys.time())
#> Prototype: datetime<local>
vec_ptype_show(factor("a"))
#> Prototype: factor<127a2>
vec_ptype_show(ordered("a"))
#> Prototype: ordered<127a2>
# Matrices ----------------------------------------------- # The prototype of a matrix includes the number of columns vec_ptype_show(array(1, dim = c(1, 2)))
#> Prototype: double[,2]
vec_ptype_show(array("x", dim = c(1, 2)))
#> Prototype: character[,2]
# Data frames -------------------------------------------- # The prototype of a data frame includes the prototype of # every column vec_ptype_show(iris)
#> Prototype: data.frame< #> Sepal.Length: double #> Sepal.Width : double #> Petal.Length: double #> Petal.Width : double #> Species : factor<12d60> #> >
# The prototype of multiple data frames includes the prototype # of every column that in any data frame vec_ptype_show( data.frame(x = TRUE), data.frame(y = 2), data.frame(z = "a") )
#> Prototype: <data.frame< #> x: logical #> y: double #> z: factor<127a2> #> >> #> 0. ( , <data.frame<x:logical>> ) = <data.frame<x:logical>> #> 1. ┌ <data.frame<x:logical>> , <data.frame<y:double>> ┐ = <data.frame< #> │ │ x: logical #> │ │ y: double #> └ ┘ >> #> 2. ┌ <data.frame< , <data.frame<z:factor<127a2>>> ┐ = <data.frame< #> │ x: logical │ x: logical #> │ y: double │ y: double #> │ >> │ z: factor<127a2> #> └ ┘ >>