Explain one row of a summary table

whence_group() takes a table from whence_table() and the number of a row. It gives a trace of that row: for each step, how many rows of its group were left, and how many the step removed. Use whence_rows() on it for the rows of the group, or for the rows of the group that one step removed.

Usage

whence_group(table, ..., row = NULL)

Arguments

table

A whence_table from whence_table().

...

The values of the group columns of the row, by name, such as region = "APAC". They must find exactly one row. A single number without a name is the number of the row.

row

The number of a row of the table. Give row, or the group values in ....

Value

A whence_group object, which is also a whence_trace. Its value is the row, as a data frame with one row.

Details

The counts come from a replay of the steps with a hidden id column. After a step that breaks the link between a row and the source, such as distinct(), the counts of the group are not known, and the trace says so. The reproduce code is the code of the table with a last filter() that keeps this row, so it gives the row as the table has it.

Examples

library(dplyr, warn.conflicts = FALSE)

by_cyl <- whence_table(
  mtcars |>
    filter(hp > 90) |>
    count(cyl)
)
six <- whence_group(by_cyl, 2)
six
#> <whence_group> cyl = 6
#> 
#> Where the rows went
#>   0 mtcars                       7
#>   1 -> hp > 90                   7
#>   2 -> summarised into this row  1
#> 
#> Reproduce
#>   mtcars |>
#>     filter(hp > 90) |>
#>     count(cyl) |>
#>     filter(cyl == 6)
whence_rows(six)
#>                 mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#> Mazda RX4      21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
#> Mazda RX4 Wag  21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
#> Hornet 4 Drive 21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
#> Valiant        18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
#> Merc 280       19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
#> Merc 280C      17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
#> Ferrari Dino   19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6

# The same row, by its group
whence_group(by_cyl, cyl = 6)
#> <whence_group> cyl = 6
#> 
#> Where the rows went
#>   0 mtcars                       7
#>   1 -> hp > 90                   7
#>   2 -> summarised into this row  1
#> 
#> Reproduce
#>   mtcars |>
#>     filter(hp > 90) |>
#>     count(cyl) |>
#>     filter(cyl == 6)