Complete matrix and parallel functions

[hadley]

Vector	Summary	Cumulative	Parallel	Matrix
+	sum	cumsum		rowSums
*	prod	cumprod
&	all	cumall
|	any	cumany
smallest()	min	cummin	pmin
greatest()	max	cummax	pmax

smallest <- function(x, y) if (x =< y) x else y
greatest <- function(x, y) if (x >= y) x else y

cf http://adv-r.had.co.nz/Functionals.html#function-family

It may be possible to avoid the matrix/row family by automatically vectorising over data frames and rows of matrices. OTOH that may be unappealing since it would mean the function sometimes summarised and sometimes transformed.

[hadley]

Particularly important for standardised NA handling

[DavisVaughan]

Also think about rolling variants of these, and how the cumulative + rolling variants could be unified under the idea of "window functions", where cumulative is just sliding with an unbounded start location. https://dbplyr.tidyverse.org/articles/translation-function.html#window-functions

(slider does all of this now with specialized variants for each summary function)

[romainfrancois]

oh interesting, so:

library(slider)

incremental_lgl <- function(x, .f, ...) {
  slide_lgl(x, .f, ..., .before = Inf)
}
incremental_lgl(c(TRUE, FALSE, TRUE), all)
#> [1]  TRUE FALSE FALSE
incremental_lgl(c(TRUE, FALSE, TRUE), any)
#> [1] TRUE TRUE TRUE


incremental_any <- function(x, ...) {
  slide_any(x, ..., before = Inf)
}
incremental_all <- function(x, ...) {
  slide_all(x, ..., before = Inf)
}
incremental_any(c(TRUE, FALSE, TRUE))
#> [1] TRUE TRUE TRUE
incremental_all(c(TRUE, FALSE, TRUE))
#> [1]  TRUE FALSE FALSE

^{Created on 2021-05-05 by the reprex package (v2.0.0)}

[romainfrancois]

library(rlang)

p <- function(.f) {
  .f <- as_function(.f)
  function(...) {
    vctrs::vec_c(!!!purrr::pmap(list2(...), .f))
  }
}
p(min)(c(1, 2), c(2, 1))
#> [1] 1 1
p(max)(c(1, 2), c(2, 1))
#> [1] 2 2
p(sum)(c(1, 2), c(2, 1))
#> [1] 3 3
p(prod)(c(1, 2), c(2, 1))
#> [1] 2 2

p(any)(c(TRUE, FALSE), c(TRUE, FALSE))
#> [1]  TRUE FALSE
p(all)(c(TRUE, FALSE), c(TRUE, FALSE))
#> [1]  TRUE FALSE

^{Created on 2021-05-05 by the reprex package (v2.0.0)}

[romainfrancois]

The "matrix" is just map() where iteration is governed by vec_slice() :

library(rlang)
library(vctrs)

dice <- function(x, .f) {
  .f <- as_function(.f)
  vec_c(!!!lapply(vec_chop(x), .f))
}

(m <- matrix(1:10, nrow = 2, byrow = TRUE))
#>      [,1] [,2] [,3] [,4] [,5]
#> [1,]    1    2    3    4    5
#> [2,]    6    7    8    9   10
dice(m, min)
#> [1] 1 6
dice(m, max)
#> [1]  5 10
dice(m, prod)
#> [1]   120 30240
dice(m, sum)
#> [1] 15 40

(m <- cbind(c(TRUE, FALSE, TRUE), c(FALSE, TRUE, TRUE)))
#>       [,1]  [,2]
#> [1,]  TRUE FALSE
#> [2,] FALSE  TRUE
#> [3,]  TRUE  TRUE
dice(m, any)
#> [1] TRUE TRUE TRUE
dice(m, all)
#> [1] FALSE FALSE  TRUE

^{Created on 2021-05-05 by the reprex package (v2.0.0)}

[DavisVaughan]

A specialized incremental_any() is probably still a decent bit faster than slide_any(x, ..., before = Inf), since the latter does much more than cumulative windows