extract, replace and combine greta arrays — extract-replace-combine • greta

Generic methods to extract and replace elements of greta arrays, or to combine greta arrays.

Arguments

x	a greta array
i, j	indices specifying elements to extract or replace
n	a single integer, as in `utils::head()` and `utils::tail()`
nrow, ncol	optional dimensions for the resulting greta array when x is not a matrix.
value	for `[<-` a greta array to replace elements, for `dim<-` either NULL or a numeric vector of dimensions
...	either further indices specifying elements to extract or replace (`[`), or multiple greta arrays to combine (`cbind()`, `rbind()` & `c()`), or additional arguments (`rep()`, `head()`, `tail()`)
drop, recursive	generic arguments that are ignored for greta arrays

Details

diag() can be used to extract or replace the diagonal part of a square and two-dimensional greta array, but it cannot be used to create a matrix-like greta array from a scalar or vector-like greta array. A static diagonal matrix can always be created with e.g. diag(3), and then converted into a greta array.

Also note that since R 4.0.0, head and tail methods for arrays changed to print a vector rather than maintain the array structure. The greta package supports both methods, and will do so based on which version of R you are using.

Usage

# extract
x[i]
x[i, j, ..., drop = FALSE]
head(x, n = 6L, ...)
tail(x, n = 6L, ...)
diag(x, nrow, ncol)
    # replace
x[i] <- value
x[i, j, ...] <- value
diag(x) <- value
    # combine
cbind(...)
rbind(...)
abind(...)
c(..., recursive = FALSE)
rep(x, times, ..., recursive = FALSE)
    # get and set dimensions
length(x)
dim(x)
dim(x) <- value

Examples

# NOT RUN {
x <- as_data(matrix(1:12, 3, 4))

# extract and replace
x[1:3, ]
x[, 2:4] <- 1:9
e <- diag(x)
diag(x) <- e + 1

# combine
cbind(x[, 2], x[, 1])
rbind(x[1, ], x[3, ])
abind(x[1, ], x[3, ], along = 1)
c(x[, 1], x)
rep(x[, 2], times = 3)
# }