3 bcast()
Inspired by the dot syntax from Julia’s broadcast() function6, bcast()/.() allows the user to execute mapply() with a convenient shorthand.
The function has two required inputs and two optional ones. The required arguments are f, the function to call, and x, the first argument over which to vectorize. The optional arguments are ..., which is a list of additional arguments to the function, and simplify, which defaults to FALSE to maintain a list type in the output–when to set to TRUE, the output is an array (typically a matrix a la` the mapply() function).
3.0.1 Broadcasting with bcast()
# GOAL: Operate across multiple matrices.
a <- matrix(1:9, 3, 3)
b <- 20:22
c <- matrix(rnorm(9), 3)
bcast(`/`, a, b, simplify = TRUE) # matrix.## [,1] [,2] [,3] [,4] [,5] [,6] [,7]
## [1,] 0.05000000 0.10000000 0.1500000 0.2000000 0.2500000 0.3000000 0.3500000
## [2,] 0.04761905 0.09523810 0.1428571 0.1904762 0.2380952 0.2857143 0.3333333
## [3,] 0.04545455 0.09090909 0.1363636 0.1818182 0.2272727 0.2727273 0.3181818
## [,8] [,9]
## [1,] 0.4000000 0.4500000
## [2,] 0.3809524 0.4285714
## [3,] 0.3636364 0.4090909## Warning in mapply(f, x, y = dots, SIMPLIFY = simplify): longer argument not a
## multiple of length of shorter## [[1]]
## [1] 0.05000000 0.04761905 0.04545455
##
## [[2]]
## [,1] [,2] [,3]
## [1,] -4.733159 -1.849731 2.228123
## [2,] -1.067596 -5.571419 5.494647
## [3,] -4.920125 291.250770 5.620815
##
## [[3]]
## [1] 0.1500000 0.1428571 0.1363636