matrix inconsistency.md

mat <- matrix(
  c(1, 2, 3, 4),
  nrow = 2
)
mat
#>      [,1] [,2]
#> [1,]    1    3
#> [2,]    2    4
indice <- integer(0) # mimic `which()` result if nothing found.
mat[-1, ] # Returns a vector... why drop = TRUE is the default? 
#> [1] 2 4
mat[-1, , drop = FALSE] # returns matrix. correctly drops first row
#>      [,1] [,2]
#> [1,]    2    4
mat[-indice, , drop = FALSE]
#>      [,1] [,2]

df <- data.frame(x = c(1, 2), y = c(1, 2))
df
#>   x y
#> 1 1 1
#> 2 2 2
df[-1, ] # correctly returns the first row
#>   x y
#> 2 2 2
df[-indice, ] # drop = FALSE is the default
#> [1] x y
#> <0 rows> (or 0-length row.names)
df[-indice, , drop = FALSE] # works okay too
#> [1] x y
#> <0 rows> (or 0-length row.names)
df[-indice, , drop = TRUE] # same as matrix
#> [1] x y
#> <0 rows> (or 0-length row.names)

^{Created on 2024-05-03 with reprex v2.1.0}

Not better for df, removes everything.. same with tibble.