Group or Select GTFS Records Without Filtering the Feed

Creates persistent selection metadata while leaving every GTFS table unchanged. Bare columns and computed values define groups, similarly to [dplyr::group_by()]. Logical expressions restrict the records represented by those groups.

Usage

selection(gtfs, ..., add = FALSE)

unselection(gtfs)

Arguments

gtfs

A GTFS object.

...

Unquoted grouping columns, computed grouping expressions, or logical selection expressions. Columns from `stop_times`, `trips`, `routes`, and `stops` are available. A `geometry` column is available for stop-based spatial predicates.

add

Logical. When `TRUE`, add the new grouping or selection expressions to an existing selection. When `FALSE`, replace it.

Value

The unchanged feed with class `wizardgtfs_selected` and a `selection` attribute. The attribute contains `groups`, `group_vars`, selected route, trip, and stop IDs, and the original expressions.

Details

A bare expression such as `route_id` creates one group per route. Multiple grouping expressions create combinations, for example `selection(gtfs, route_id, direction_id)`. Logical expressions such as `route_id %in% c("1", "2")` restrict the records represented in the selection but do not remove rows from the GTFS feed.

Spatial expressions may use `geometry` with `%intersects%`, `%touches%`, `%crosses%`, `%within%`, `%contains%`, `%overlaps%`, or `%equals%`.

See also

[GTFSwizard::unselection()], [dplyr::group_by()]

Examples

grouped <- selection(for_rail_gtfs, route_id, direction_id)
attr(grouped, "selection")$groups
#> # A tibble: 6 × 6
#>   route_id direction_id n_stop_calls routes    trips      stops     
#>   <chr>           <int>        <int> <list>    <list>     <list>    
#> 1 6                   0         1260 <chr [1]> <chr [63]> <chr [20]>
#> 2 6                   1         1280 <chr [1]> <chr [64]> <chr [20]>
#> 3 7                   0          150 <chr [1]> <chr [15]> <chr [10]>
#> 4 7                   1          150 <chr [1]> <chr [15]> <chr [10]>
#> 5 8                   0          290 <chr [1]> <chr [29]> <chr [10]>
#> 6 8                   1          290 <chr [1]> <chr [29]> <chr [10]>

selected <- selection(
  for_rail_gtfs,
  route_id,
  stop_id %in% for_rail_gtfs$stops$stop_id[1:3]
)

bbox <- sf::st_bbox(
  c(xmin = -38.58, ymin = -3.81, xmax = -38.50, ymax = -3.75),
  crs = sf::st_crs(4326)
)
spatial <- selection(
  for_rail_gtfs,
  geometry %intersects% sf::st_as_sfc(bbox)
)