Add a column of ntiles to a data table

Add a column of ntiles to a data table

mutate_ntile(DT, col, n, weights = NULL, by = NULL, keyby = NULL,
  new.col = NULL, character.only = FALSE, overwrite = TRUE,
  check.na = FALSE)

Arguments

DT	A data.table.
col	The column name (quoted or unquoted) for which quantiles are desired.
n	A positive integer, the number of groups to split col.
weights	If NULL, the default, use unweighted quantiles. Otherwise, a string designating the column that is passed to weighted_ntile.
by, keyby	Produce a grouped quantile column, as in data.table. keyby will set a key on the result (i.e. order by keyby).
new.col	If not NULL, the name of the column to be added. If NULL (the default) a name will be inferred from n. (For example, n = 100 will be <col>Percentile).
character.only	(logical, default: FALSE) Do not contemplate col to be an unquoted column name.
overwrite	(logical, default: TRUE) If TRUE and new.col already exists in DT, the column will be overwritten. If FALSE, attempting to overwrite an existing column is an error.
check.na	(logical, default: FALSE) If TRUE, NAs in DT[[col]] will throw an error. If NA's are present, the corresponding n-tile may take any value.

Value

DT with a new integer column new.col containing the quantiles. If DT is not a data.table its class may be preserved unless keyby is used, where it will always be a data.table.

Examples

library(data.table)
DT <- data.table(x = 1:20, y = 2:1)
mutate_ntile(DT, "x", n = 10)
#>      x y xDecile
#>  1:  1 2       1
#>  2:  2 1       1
#>  3:  3 2       2
#>  4:  4 1       2
#>  5:  5 2       3
#>  6:  6 1       3
#>  7:  7 2       4
#>  8:  8 1       4
#>  9:  9 2       5
#> 10: 10 1       5
#> 11: 11 2       6
#> 12: 12 1       6
#> 13: 13 2       7
#> 14: 14 1       7
#> 15: 15 2       8
#> 16: 16 1       8
#> 17: 17 2       9
#> 18: 18 1       9
#> 19: 19 2      10
#> 20: 20 1      10
mutate_ntile(DT, "x", n = 5)
#>      x y xDecile xQuintile
#>  1:  1 2       1         1
#>  2:  2 1       1         1
#>  3:  3 2       2         1
#>  4:  4 1       2         1
#>  5:  5 2       3         2
#>  6:  6 1       3         2
#>  7:  7 2       4         2
#>  8:  8 1       4         2
#>  9:  9 2       5         3
#> 10: 10 1       5         3
#> 11: 11 2       6         3
#> 12: 12 1       6         3
#> 13: 13 2       7         4
#> 14: 14 1       7         4
#> 15: 15 2       8         4
#> 16: 16 1       8         4
#> 17: 17 2       9         5
#> 18: 18 1       9         5
#> 19: 19 2      10         5
#> 20: 20 1      10         5
mutate_ntile(DT, "x", n = 10, by = "y")
#>      x y xDecile xQuintile
#>  1:  1 2       1         1
#>  2:  2 1       1         1
#>  3:  3 2       2         1
#>  4:  4 1       2         1
#>  5:  5 2       3         2
#>  6:  6 1       3         2
#>  7:  7 2       4         2
#>  8:  8 1       4         2
#>  9:  9 2       5         3
#> 10: 10 1       5         3
#> 11: 11 2       6         3
#> 12: 12 1       6         3
#> 13: 13 2       7         4
#> 14: 14 1       7         4
#> 15: 15 2       8         4
#> 16: 16 1       8         4
#> 17: 17 2       9         5
#> 18: 18 1       9         5
#> 19: 19 2      10         5
#> 20: 20 1      10         5
mutate_ntile(DT, "x", n = 10, keyby = "y")
#>      x y xDecile xQuintile
#>  1:  2 1       1         1
#>  2:  4 1       2         1
#>  3:  6 1       3         2
#>  4:  8 1       4         2
#>  5: 10 1       5         3
#>  6: 12 1       6         3
#>  7: 14 1       7         4
#>  8: 16 1       8         4
#>  9: 18 1       9         5
#> 10: 20 1      10         5
#> 11:  1 2       1         1
#> 12:  3 2       2         1
#> 13:  5 2       3         2
#> 14:  7 2       4         2
#> 15:  9 2       5         3
#> 16: 11 2       6         3
#> 17: 13 2       7         4
#> 18: 15 2       8         4
#> 19: 17 2       9         5
#> 20: 19 2      10         5

y <- "x"
DT <- data.table(x = 1:20, y = 2:1)
mutate_ntile(DT, y, n = 5)                        # Use DT$y
#> Warning: Interpreting `col = y` as column `DT[['y']]`, not column `DT[['x']]`, despite an extant object y.
#>      x y yQuintile
#>  1:  1 2         3
#>  2:  2 1         1
#>  3:  3 2         3
#>  4:  4 1         1
#>  5:  5 2         4
#>  6:  6 1         1
#>  7:  7 2         4
#>  8:  8 1         1
#>  9:  9 2         4
#> 10: 10 1         2
#> 11: 11 2         4
#> 12: 12 1         2
#> 13: 13 2         5
#> 14: 14 1         2
#> 15: 15 2         5
#> 16: 16 1         2
#> 17: 17 2         5
#> 18: 18 1         3
#> 19: 19 2         5
#> 20: 20 1         3
mutate_ntile(DT, y, n = 5, character.only = TRUE) # Use DT$x
#>      x y yQuintile xQuintile
#>  1:  1 2         3         1
#>  2:  2 1         1         1
#>  3:  3 2         3         1
#>  4:  4 1         1         1
#>  5:  5 2         4         2
#>  6:  6 1         1         2
#>  7:  7 2         4         2
#>  8:  8 1         1         2
#>  9:  9 2         4         3
#> 10: 10 1         2         3
#> 11: 11 2         4         3
#> 12: 12 1         2         3
#> 13: 13 2         5         4
#> 14: 14 1         2         4
#> 15: 15 2         5         4
#> 16: 16 1         2         4
#> 17: 17 2         5         5
#> 18: 18 1         3         5
#> 19: 19 2         5         5
#> 20: 20 1         3         5