Vector recycling — vec_recycle • vctrs

vec_recycle(x, size) recycles a single vector to given size. vec_recycle_common(...) recycles multiple vectors to their common size. All functions obey the vctrs recycling rules, described below, and will throw an error if recycling is not possible. See vec_size() for the precise definition of size.

Usage

vec_recycle(x, size, ..., x_arg = "", call = caller_env())

vec_recycle_common(..., .size = NULL, .arg = "", .call = caller_env())

Arguments

x

A vector to recycle.

size

Desired output size.

...

For vec_recycle_common(), vectors to recycle.
- For vec_recycle(), these dots should be empty.

x_arg

Argument name for x. These are used in error messages to inform the user about which argument has an incompatible size.

call, .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.

.size

Desired output size. If omitted, will use the common size from vec_size_common().

.arg

An argument name as a string. This argument will be mentioned in error messages as the input that is at the origin of a problem.

Recycling rules

The common size of two vectors defines the recycling rules, and can be summarise with the following table:

(Note NULLs are handled specially; they are treated like empty arguments and hence don't affect the size)

This is a stricter set of rules than base R, which will usually return output of length max(nx, ny), warning if the length of the longer vector is not an integer multiple of the length of the shorter.

We say that two vectors have compatible size if they can be recycled to be the same length.

Dependencies

vec_slice()

Examples

# Inputs with 1 observation are recycled
vec_recycle_common(1:5, 5)
#> [[1]]
#> [1] 1 2 3 4 5
#> 
#> [[2]]
#> [1] 5 5 5 5 5
#> 
vec_recycle_common(integer(), 5)
#> [[1]]
#> integer(0)
#> 
#> [[2]]
#> numeric(0)
#> 
if (FALSE) {
vec_recycle_common(1:5, 1:2)
}

# Data frames and matrices are recycled along their rows
vec_recycle_common(data.frame(x = 1), 1:5)
#> [[1]]
#>   x
#> 1 1
#> 2 1
#> 3 1
#> 4 1
#> 5 1
#> 
#> [[2]]
#> [1] 1 2 3 4 5
#> 
vec_recycle_common(array(1:2, c(1, 2)), 1:5)
#> [[1]]
#>      [,1] [,2]
#> [1,]    1    2
#> [2,]    1    2
#> [3,]    1    2
#> [4,]    1    2
#> [5,]    1    2
#> 
#> [[2]]
#> [1] 1 2 3 4 5
#> 
vec_recycle_common(array(1:3, c(1, 3, 1)), 1:5)
#> [[1]]
#> , , 1
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    2    3
#> [2,]    1    2    3
#> [3,]    1    2    3
#> [4,]    1    2    3
#> [5,]    1    2    3
#> 
#> 
#> [[2]]
#> [1] 1 2 3 4 5
#>