`vec_rep()`

repeats an entire vector a set number of`times`

.`vec_rep_each()`

repeats each element of a vector a set number of`times`

.`vec_unrep()`

compresses a vector with repeated values. The repeated values are returned as a`key`

alongside the number of`times`

each key is repeated.

## Arguments

- x
A vector.

- times
For

`vec_rep()`

, a single integer for the number of times to repeat the entire vector.For

`vec_rep_each()`

, an integer vector of the number of times to repeat each element of`x`

.`times`

will be recycled to the size of`x`

.

## Value

For `vec_rep()`

, a vector the same type as `x`

with size
`vec_size(x) * times`

.
For `vec_rep_each()`

, a vector the same type as `x`

with size
`sum(vec_recycle(times, vec_size(x)))`

.
For `vec_unrep()`

, a data frame with two columns, `key`

and `times`

. `key`

is a vector with the same type as `x`

, and `times`

is an integer vector.

## Details

Using `vec_unrep()`

and `vec_rep_each()`

together is similar to using
`base::rle()`

and `base::inverse.rle()`

. The following invariant shows
the relationship between the two functions:

```
compressed <- vec_unrep(x)
identical(x, vec_rep_each(compressed$key, compressed$times))
```

There are two main differences between `vec_unrep()`

and `base::rle()`

:

## Examples

```
# Repeat the entire vector
vec_rep(1:2, 3)
#> [1] 1 2 1 2 1 2
# Repeat within each vector
vec_rep_each(1:2, 3)
#> [1] 1 1 1 2 2 2
x <- vec_rep_each(1:2, c(3, 4))
x
#> [1] 1 1 1 2 2 2 2
# After using `vec_rep_each()`, you can recover the original vector
# with `vec_unrep()`
vec_unrep(x)
#> key times
#> 1 1 3
#> 2 2 4
df <- data.frame(x = 1:2, y = 3:4)
# `rep()` repeats columns of data frames, and returns lists
rep(df, each = 2)
#> $x
#> [1] 1 2
#>
#> $x
#> [1] 1 2
#>
#> $y
#> [1] 3 4
#>
#> $y
#> [1] 3 4
#>
# `vec_rep()` and `vec_rep_each()` repeat rows, and return data frames
vec_rep(df, 2)
#> x y
#> 1 1 3
#> 2 2 4
#> 3 1 3
#> 4 2 4
vec_rep_each(df, 2)
#> x y
#> 1 1 3
#> 2 1 3
#> 3 2 4
#> 4 2 4
# `rle()` treats adjacent missing values as different
y <- c(1, NA, NA, 2)
rle(y)
#> Run Length Encoding
#> lengths: int [1:4] 1 1 1 1
#> values : num [1:4] 1 NA NA 2
# `vec_unrep()` treats them as equivalent
vec_unrep(y)
#> key times
#> 1 1 1
#> 2 NA 2
#> 3 2 1
```