Intro to csutil

Splitting

easy_split() divides a vector into groups either by specifying the target size of each group or the total number of groups.

csutil::easy_split(letters[1:20], size_of_each_group = 3)
#> $`1`
#> [1] "a" "b" "c"
#> 
#> $`2`
#> [1] "d" "e" "f"
#> 
#> $`3`
#> [1] "g" "h" "i"
#> 
#> $`4`
#> [1] "j" "k" "l"
#> 
#> $`5`
#> [1] "m" "n" "o"
#> 
#> $`6`
#> [1] "p" "q" "r"
#> 
#> $`7`
#> [1] "s" "t"
csutil::easy_split(letters[1:20], number_of_groups = 3)
#> $`1`
#> [1] "a" "b" "c" "d" "e" "f" "g"
#> 
#> $`2`
#> [1] "h" "i" "j" "k" "l" "m" "n"
#> 
#> $`3`
#> [1] "o" "p" "q" "r" "s" "t"

Unnesting data frames within a list

unnest_dfs_within_list_of_fully_named_lists() collapses a list of named lists, each containing data frames, into a single flat list. Elements that share a name across the outer lists are row-bound together.

x <- list(
  list(
    "a" = data.frame("v1"=1),
    "b" = data.frame("v2"=3)
  ),
  list(
    "a" = data.frame("v1"=10),
    "b" = data.frame("v2"=30),
    "d" = data.frame("v3"=50)
  )
)
print(x)
#> [[1]]
#> [[1]]$a
#>   v1
#> 1  1
#> 
#> [[1]]$b
#>   v2
#> 1  3
#> 
#> 
#> [[2]]
#> [[2]]$a
#>   v1
#> 1 10
#> 
#> [[2]]$b
#>   v2
#> 1 30
#> 
#> [[2]]$d
#>   v3
#> 1 50
csutil::unnest_dfs_within_list_of_fully_named_lists(x)
#> $a
#>       v1
#>    <num>
#> 1:     1
#> 2:    10
#> 
#> $b
#>       v2
#>    <num>
#> 1:     3
#> 2:    30
#> 
#> $d
#>       v3
#>    <num>
#> 1:    50

Describing lists

These predicates test structural properties of a list: whether every element is named, and whether every element is NULL or a particular type.

csutil::is_fully_named_list(list(1))
#> [1] FALSE
csutil::is_fully_named_list(list("a"=1))
#> [1] TRUE

csutil::is_all_list_elements_null_or_df(list(data.frame()))
#> [1] TRUE
csutil::is_all_list_elements_null_or_df(list(1, NULL))
#> [1] FALSE

csutil::is_all_list_elements_null_or_list(list(1, NULL))
#> [1] FALSE
csutil::is_all_list_elements_null_or_list(list(list(), NULL))
#> [1] TRUE

csutil::is_all_list_elements_null_or_fully_named_list(list(list(), NULL))
#> [1] FALSE
csutil::is_all_list_elements_null_or_fully_named_list(list(list("a" = 1), NULL))
#> [1] TRUE

Applying a function via hash table

apply_fn_via_hash_table() extracts the unique values from the input, applies the given function once per unique value to build a lookup table, then maps the results back to the original input. When there are many repeated values, this avoids redundant computation and can be substantially faster than applying the function element-wise.

input <- rep(seq(as.Date("2000-01-01"), as.Date("2020-01-01"), 1), 1000)
a1 <- Sys.time()
z <- format(input, "%Y")
a2 <- Sys.time()
a2 - a1
#> Time difference of 2.378592 secs

b1 <- Sys.time()
z <- csutil::apply_fn_via_hash_table(
  input,
  format,
  "%Y"
)
b2 <- Sys.time()
b2 - b1
#> Time difference of 0.4031551 secs