greta (version 0.4.5)

extract-replace-combine: extract, replace and combine greta arrays

Description

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

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

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.

Examples

if (FALSE) {

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)
}