Like dplyr::group_by(), but for patterns. tar_group() allows you to map or cross over subsets of data frames. Requires iteration = "group" on the target. See the example.

tar_group(x)

Arguments

x

Grouped data frame from dplyr::group_by()

Value

A data frame with a special tar_group column that targets will use to find subsets of your data frame.

Details

The goal of tar_group() is to post-process the return value of a data frame target to allow downstream targets to branch over subsets of rows. It takes the groups defined by dplyr::group_by() and translates that information into a special tar_group is a column. tar_group is a vector of positive integers from 1 to the number of groups. Rows with the same integer in tar_group belong to the same group, and branches are arranged in increasing order with respect to the integers in tar_group. The assignment of tar_group integers to group levels depends on the orderings inside the grouping variables and not the order of rows in the dataset. dplyr::group_keys() on the grouped data frame shows how the grouping variables correspond to the integers in the tar_group column.

See also

Other utilities: tar_cancel(), tar_definition(), tar_envir(), tar_name(), tar_path(), tar_seed()

Examples

if (identical(Sys.getenv("TAR_EXAMPLES"), "true")) { # The tar_group() function simply creates # a tar_group column to partition the rows # of a data frame. data.frame( x = seq_len(6), id = rep(letters[seq_len(3)], each = 2) ) %>% dplyr::group_by(id) %>% tar_group() # We use tar_group() below to branch over # subsets of a data frame defined with dplyr::group_by(). tar_dir({ # tar_dir() runs code from a temporary directory. tar_script({ library(dplyr) list( tar_target( data, data.frame( x = seq_len(6), id = rep(letters[seq_len(3)], each = 2) ) %>% group_by(id) %>% tar_group(), iteration = "group" ), tar_target( sums, sum(data$x), pattern = map(data), iteration = "vector" ) ) }) tar_make() tar_read(sums) # Should be c(3, 7, 11). }) }