R Under development (unstable) (2023-11-06 r85483 ucrt) -- "Unsuffered Consequences"
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Platform: x86_64-w64-mingw32/x64

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> library("matrixStats")
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Consistency checks
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> set.seed(1)
> 
> mean2_R <- function(x, na.rm = FALSE, idxs = NULL) {
+   if (is.null(idxs)) {
+     mean(x, na.rm = na.rm)
+   } else {
+     mean(x[idxs], na.rm = na.rm)
+   }
+ } # mean2_R()
> 
> 
> cat("Consistency checks:\n")
Consistency checks:
> for (kk in 1:20) {
+   cat("Random test #", kk, "\n", sep = "")
+ 
+   # Simulate data in a matrix of any shape
+   n <- sample(100L, size = 1L)
+   x <- rnorm(n, sd = 100)
+ 
+   # Add NAs?
+   if ((kk %% 4) %in% c(3, 0)) {
+     cat("Adding NAs\n")
+     nna <- sample(n, size = 1L)
+     na_values <- c(NA_real_, NaN)
+     t <- sample(na_values, size = nna, replace = TRUE)
+     x[sample(length(x), size = nna)] <- t
+   }
+ 
+   # Integer or double?
+   if ((kk %% 4) %in% c(2, 0)) {
+     cat("Coercing to integers\n")
+     storage.mode(x) <- "integer"
+   }
+ 
+   na.rm <- sample(c(TRUE, FALSE), size = 1L)
+ 
+   # Sum over all
+   y0 <- mean2_R(x, na.rm = na.rm)
+   y1 <- mean2(x, na.rm = na.rm)
+   stopifnot(all.equal(y1, y0))
+ 
+   # Sum over subset
+   nidxs <- sample(n, size = 1L)
+   idxs <- sample(n, size = nidxs)
+   y0 <- mean2_R(x, na.rm = na.rm, idxs = idxs)
+   y1 <- mean2(x, na.rm = na.rm, idxs = idxs)
+   stopifnot(all.equal(y1, y0))
+ 
+   if (storage.mode(x) == "integer") {
+     storage.mode(x) <- "logical"
+     
+     y0 <- mean2_R(x, na.rm = na.rm)
+     y1 <- mean2(x, na.rm = na.rm)
+     stopifnot(all.equal(y1, y0))
+     
+     y0 <- mean2_R(x, na.rm = na.rm, idxs = idxs)
+     y1 <- mean2(x, na.rm = na.rm, idxs = idxs)
+     stopifnot(all.equal(y1, y0))
+   }
+ } # for (kk ...)
Random test #1
Random test #2
Coercing to integers
Random test #3
Adding NAs
Random test #4
Adding NAs
Coercing to integers
Random test #5
Random test #6
Coercing to integers
Random test #7
Adding NAs
Random test #8
Adding NAs
Coercing to integers
Random test #9
Random test #10
Coercing to integers
Random test #11
Adding NAs
Random test #12
Adding NAs
Coercing to integers
Random test #13
Random test #14
Coercing to integers
Random test #15
Adding NAs
Random test #16
Adding NAs
Coercing to integers
Random test #17
Random test #18
Coercing to integers
Random test #19
Adding NAs
Random test #20
Adding NAs
Coercing to integers
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Special cases
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> for (na.rm in c(FALSE, TRUE)) {
+   # Averaging over zero elements (integers)
+   x <- integer(0)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   x <- 1:5
+   idxs <- integer(0)
+   s1 <- mean(x[idxs], na.rm = na.rm)
+   s2 <- mean2(x, idxs = idxs, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over NA_integer_:s
+   x <- rep(NA_integer_, times = 5L)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   x <- rep(NA_integer_, times = 5L)
+   idxs <- 1:3
+   s1 <- mean(x[idxs], na.rm = na.rm)
+   s2 <- mean2(x, idxs = idxs, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+ 
+   # Averaging over zero elements (doubles)
+   x <- double(0)
+   s1 <- mean(x)
+   s2 <- mean2(x)
+   stopifnot(identical(s1, s2))
+ 
+   x <- as.double(1:10)
+   idxs <- integer(0)
+   s1 <- mean(x[idxs])
+   s2 <- mean2(x, idxs = idxs)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over NA_real_:s
+   x <- rep(NA_real_, times = 5L)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   x <- rep(NA_real_, times = 5L)
+   idxs <- 1:3
+   s1 <- mean(x[idxs], na.rm = na.rm)
+   s2 <- mean2(x, idxs = idxs, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over -Inf:s
+   x <- rep(-Inf, times = 3L)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over +Inf:s
+   x <- rep(+Inf, times = 3L)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over mix of -Inf:s and +Inf:s
+   x <- rep(c(-Inf, +Inf), times = 3L)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over mix of -Inf:s and +Inf:s and numerics
+   x <- rep(c(-Inf, +Inf, 3.14), times = 2L)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   stopifnot(identical(s1, s2))
+ 
+   # Averaging over mix of NaN, NA, +Inf, and numerics
+   x <- c(NaN, NA, +Inf, 3.14)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   if (na.rm) {
+     stopifnot(identical(s2, s1))
+   } else {
+     stopifnot(is.na(s1), is.na(s2))
+     ## NOTE, due to compiler optimization, it is not guaranteed that NA is
+     ## returned here (as one would expect). NaN might very well be returned,
+     ## when both NA and NaN are involved.  This is an accepted feature in R,
+     ## which is documented in help("is.nan").  See also
+     ## https://stat.ethz.ch/pipermail/r-devel/2017-April/074009.html.
+     ## Thus, we cannot guarantee that s1 is identical to s0.
+   }
+ 
+   # Averaging over mix of NaN, NA_real_, +Inf, and numerics
+   x <- c(NA_real_, NaN, +Inf, 3.14)
+   s1 <- mean(x, na.rm = na.rm)
+   s2 <- mean2(x, na.rm = na.rm)
+   if (na.rm) {
+     stopifnot(identical(s2, s1))
+   } else {
+     stopifnot(is.na(s1), is.na(s2))
+     ## NOTE, due to compiler optimization, it is not guaranteed that NA is
+     ## returned here (as one would expect). NaN might very well be returned,
+     ## when both NA and NaN are involved.  This is an accepted feature in R,
+     ## which is documented in help("is.nan").  See also
+     ## https://stat.ethz.ch/pipermail/r-devel/2017-April/074009.html.
+     ## Thus, we cannot guarantee that s1 is identical to s0.
+   }
+ }
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Argument 'idxs'
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> x <- 1:5
> idxs_list <- list(
+   integer = 1:3,
+   double  = as.double(1:3),
+   logical = (x <= 3)
+ )
> 
> for (idxs in idxs_list) {
+   cat("idxs:\n")
+   str(idxs)
+   s1 <- mean(x[idxs], na.rm = TRUE)
+   s2 <- mean2(x, idxs = idxs, na.rm = TRUE)
+   stopifnot(identical(s1, s2))
+ }
idxs:
 int [1:3] 1 2 3
idxs:
 num [1:3] 1 2 3
idxs:
 logi [1:5] TRUE TRUE TRUE FALSE FALSE
> 
> proc.time()
   user  system elapsed 
   0.17    0.10    0.26