Create Nested Group Header Rows in a data.table

Transforms a data.table by inserting header rows for each level of the specified grouping variables. The grouping variables are moved to the front of the dataset.

Usage

group_data(data, groups, shift_to = NULL, indent = FALSE, carry = NULL)

Arguments

data

A data.table. If a data.frame is provided, it will be converted.

groups

A character vector of column names to group by (ordered high to low).

shift_to

Character. The name of the column into which group labels are shifted. When NULL (default) no shifting is performed.

indent

Logical. If TRUE, indents nested headers and data rows.

carry

Character vector of column names whose values should be carried into header rows rather than set to NA. Each named column must have a unique value within its group at every nesting level - an error is thrown if that is not the case.

Value

A data.table with nested header rows.

Examples

library(data.table)
#> 
#> Attaching package: ‘data.table’
#> The following object is masked from ‘package:base’:
#> 
#>     %notin%
dt <- data.table(Region = c("North", "North", "South"),
                 Dept = c("Sales", "Sales", "HR"),
                 Staff = c("A", "B", "C"),
                 Sales = c(10, 20, 30))

# Standard headers
group_data(dt, groups = "Region")
#>    Region   Dept  Staff Sales
#>    <char> <char> <char> <num>
#> 1:  North   <NA>   <NA>    NA
#> 2:  North  Sales      A    10
#> 3:  North  Sales      B    20
#> 4:  South   <NA>   <NA>    NA
#> 5:  South     HR      C    30

# Shifted and indented headers for reporting
group_data(dt, groups = "Region", shift_to = "Staff", indent = TRUE)
#>      Dept  Staff Sales
#>    <char> <char> <num>
#> 1:   <NA>  North    NA
#> 2:  Sales      A    10
#> 3:  Sales      B    20
#> 4:   <NA>  South    NA
#> 5:     HR      C    30
# Shifted and indented headers for reporting with multiple grouping levels
group_data(dt, groups = c("Region", "Dept"), shift_to = "Staff", indent = TRUE)
#>       Staff Sales
#>      <char> <num>
#> 1:    North    NA
#> 2:    Sales    NA
#> 3:        A    10
#> 4:        B    20
#> 5:    South    NA
#> 6:       HR    NA
#> 7:        C    30