rray_yank() gets and sets elements from an array by position. It is the
complement to rray_extract(), which gets and sets elements by index.
For rrays, [[ is powered by rray_yank(), and allows you to
select multiple elements by position with the syntax: x[[i]].
There are three assignment variations that all work essentially the same.
They ensures that value has the same inner type as x, and value must be
1D.
rray_yank(x, i) <- value
x[[i]] <- value
rray_yank_assign(x, i, value)
rray_yank(x, i) <- value # S3 method for vctrs_rray [[(x, i, ...) <- value rray_yank_assign(x, i, value) rray_yank(x, i) # S3 method for vctrs_rray [[(x, i, ...)
| x | A vector, matrix, array or rray. |
|---|---|
| i | One of the following:
|
| value | A 1D value to be assigned to the location yanked by |
| ... | Not used. An error is thrown if extra arguments are supplied here. |
A 1D vector of elements yanked out of x.
rray_yank() is meant as a replacement for the traditional behavior of
x[i], which extracts multiple elements by their position, and returns a
1D vector. rray is much stricter, and for rrays x[i] would return the
i rows of x, without dropping any dimensions. Separating this special
behavior of extracting by position into a new function is less surprising,
and allows [ to be more consistent and stable.
rray_yank() never keeps dimension names. For >1D objects, this would not
be well defined to begin with, so the decision was made to keep this behavior
for 1D objects as well. Think of rray_yank() as a way to rip out the inner
elements of x. The dimension names and outer type are not a part of
this information.
[[rray_yank() powers [[ for rray objects. It works a bit differently from
base R. As with [, base R allows [[ to perform two roles. It can extract
one element by position with x[[i]], or one element by index with
x[[i, j, ...]]. This felt too flexible, so with rray objects [[ is
directly powered by rray_yank(), meaning it can only do x[[i]]. However,
multiple values of i are allowed, rather than just 1, meaning that
x[[c(3, 5)]] will extract the 3rd and 5th positions in x and return
them as a 1D array.
Notably this means that the index extraction behavior of x[[i, j, ...]]
is missing with [[ for rrays. If you want that behavior,
see rray_extract().
Other rray subsetters: rray_extract<-,
rray_slice<-, rray_subset<-
x <- rray(10:17, c(2, 2, 2)) # Resulting dimension is always 1D, and is a base R array rray_yank(x, 1:3)#> [1] 10 11 12# Subsetting with a logical is possible if it is either # length 1 or the length of `x` rray_yank(x, FALSE)#> integer(0)#> [1] 10 12 14 16# You can assign a 1D vector to these yanked selections # Length 1 values are recycled as required rray_yank(x, c(1, 3, 5)) <- 9 # `rray_yank()` powers `[[` as well # Notably, you can yank multiple values in `[[` x[[c(1, 3, 5)]] <- NA # Logicals with the same dim as `x` can also be used as a yank indexer # This comes in handy as a way to remove NA values x[[is.na(x)]] <- 0