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

In greta: Simple and 'Scalable' Statistical Modelling in R

extract, replace and combine greta arrays

Description

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

Usage

## S3 method for class 'greta_array'
x[...]

## S3 replacement method for class 'greta_array'
x[...] <- value

## S3 method for class 'greta_array'
cbind(...)

## S3 method for class 'greta_array'
rbind(...)

## S3 method for class 'greta_array'
c(...)

## S3 method for class 'greta_array'
rep(x, ...)

## S3 method for class 'greta_array'
dim(x)

## S3 method for class 'greta_array'
length(x)

## S3 replacement method for class 'greta_array'
dim(x) <- value

## S3 method for class 'greta_array'
head(x, n = 6L, ...)

## S3 method for class 'greta_array'
tail(x, n = 6L, ...)

## S3 method for class 'greta_array'
diag(x = 1, nrow, ncol)

Arguments

x	a greta array
...	either further indices specifying elements to extract or replace (i, j for [), or multiple greta arrays to combine (cbind(), rbind() & c()), or additional arguments (rep(), head(), tail()). Generic arguments such as drop and recursive are accepted but ignored for greta arrays.
value	for ⁠[<-⁠ a greta array to replace elements, for ⁠dim<-⁠ either NULL or a numeric vector of dimensions
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.

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.

Value

A greta_array, with elements extracted, replaced, or combined as appropriate for the method called.

Syntax

These methods can be used with greta arrays as follows:

# 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)

## End(Not run)

greta documentation built on July 20, 2026, 5:09 p.m.