rray_broadcast: Broadcast to a new dimension

In rray: Simple Arrays

Description

rray_broadcast() will broadcast the dimensions of the current object to a new dimension.

Usage

rray_broadcast(x, dim)

Arguments

x	The object to broadcast.
dim	An integer vector. The dimension to broadcast to.

Details

Broadcasting works by recycling dimensions and repeating values in those dimensions to match the new dimension.

Here's an example. Assume you have a 1x3 matrix that you want to broadcast to a dimension of 2x3. Since the 1st dimensions are different, and one of them is 1, the 1 row of the 1x3 matrix is repeated to become a 2x3 matrix. For the second dimension, both are already 3 so nothing is done.

(1, 3)
(2, 3)
------
(2, 3)

As an example that doesn't broadcast, here is an attempt to make a 2x1x4 matrix broadcast to a 2x3x5 matrix (In the R world, 2x3x4 means a 2 row, 3 column, and 4 "deep" array). The first 2 dimensions are fine, but for the third dimension, 4 and 5 are not "recyclable" and are therefore incompatible.

(2, 1, 4)
(2, 3, 5)
---------
(2, 3, X)

You can broadcast to higher dimensions too. If you go from a 5x2 to a 5x2x3 array, then the 5x2 matrix implicitly gets a 1 appended as another dimension (i.e. 5x2x1)

(5, 2,  ) <- implicit 1 is recycled
(5, 2, 3)
---------
(5, 2, 3)

Broadcasting is an important concept in rray, as it is the engine behind the different structure for arithmetic operations.

Value

x broadcast to the new dimensions.

Examples

# From 5x1 ...
x <- rray(1:5)

# ...to 5x2
rray_broadcast(x, c(5, 2))

# Internally, rray() uses broadcasting
# for convenience so you could have also
# done this with:
rray(1:5, dim = c(5, 2))

# Moar dimensions
rray_broadcast(x, c(5, 2, 3))

# You cannot broadcast down in dimensions
try(rray_broadcast(x, 5))

rray documentation built on July 23, 2019, 5:04 p.m.