Repeat a vector
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.
vec_rep(x, times) vec_rep_each(x, times) vec_unrep(x)
x |
A vector. |
times |
For For |
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():
vec_unrep() treats adjacent missing values as equivalent, while rle()
treats them as different values.
vec_unrep() works along the size of x, while rle() works along its
length. This means that vec_unrep() works on data frames by compressing
repeated rows.
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.
# Repeat the entire vector vec_rep(1:2, 3) # Repeat within each vector vec_rep_each(1:2, 3) x <- vec_rep_each(1:2, c(3, 4)) x # After using `vec_rep_each()`, you can recover the original vector # with `vec_unrep()` vec_unrep(x) df <- data.frame(x = 1:2, y = 3:4) # `rep()` repeats columns of data frames, and returns lists rep(df, each = 2) # `vec_rep()` and `vec_rep_each()` repeat rows, and return data frames vec_rep(df, 2) vec_rep_each(df, 2) # `rle()` treats adjacent missing values as different y <- c(1, NA, NA, 2) rle(y) # `vec_unrep()` treats them as equivalent vec_unrep(y)
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