gtfs_isochrone — gtfs_isochrone • gtfsrouter

Calculate a single isochrone from a given start station, returning the list of all stations reachable to the specified end_time.

gtfs_isochrone(
  gtfs,
  from,
  start_time,
  end_time,
  day = NULL,
  from_is_id = FALSE,
  route_pattern = NULL,
  hull_alpha = 0.1,
  quiet = FALSE
)

Arguments

gtfs	A set of GTFS data returned from extract_gtfs or, for more efficient queries, pre-processed with gtfs_timetable.
from	Name, ID, or approximate (lon, lat) coordinates of start station (as `stop_name` or `stop_id` entry in the `stops` table, or a vector of two numeric values).
start_time	Desired departure time at `from` station, either in seconds after midnight, a vector of two or three integers (hours, minutes) or (hours, minutes, seconds), an object of class difftime, hms, or lubridate.
end_time	End time to calculate isochrone
day	Day of the week on which to calculate route, either as an unambiguous string (so "tu" and "th" for Tuesday and Thursday), or a number between 1 = Sunday and 7 = Saturday. If not given, the current day will be used. (Not used if `gtfs` has already been prepared with gtfs_timetable.)
from_is_id	Set to `TRUE` to enable `from` parameter to specify entry in `stop_id` rather than `stop_name` column of the `stops` table (same as `from_to_are_ids` parameter of gtfs_route).
route_pattern	Using only those routes matching given pattern, for example, "^U" for routes starting with "U" (as commonly used for underground or subway routes. (Parameter not used at all if `gtfs` has already been prepared with gtfs_timetable.)
hull_alpha	alpha value of non-convex hulls returned as part of result (see ?alphashape::ashape for details).
quiet	Set to `TRUE` to suppress screen messages (currently just regarding timetable construction).

Value

An object of class gtfs_isochrone, including sf-formatted points representing the from station (start_point), the terminal end stations (end_points), and all intermediate stations (mid_points) each with the earliest possible arrival time, along with lines representing the individual routes. A non-convex ("alpha") hull is also returned (as an sf POLYGON object), including measures of area and "elongation", which equals zero for a circle, and increases towards one for more elongated shapes.

Examples

berlin_gtfs_to_zip ()
f <- file.path (tempdir (), "vbb.zip")
g <- extract_gtfs (f)
#> ▶ Unzipping GTFS archive
#> 
✔ Unzipped GTFS archive  
#> ▶ Extracting GTFS feed
#> 
✔ Extracted GTFS feed 
#> ▶ Converting stop times to seconds
#> 
✔ Converted stop times to seconds 
#> ▶ Converting transfer times to seconds
#> 
✔ Converted transfer times to seconds 
g <- gtfs_timetable (g)
#> Day not specified; extracting timetable for Monday
from <- "Alexanderplatz"
start_time <- 12 * 3600 + 600
end_time <- start_time + 600
ic <- gtfs_isochrone (g,
                      from = from,
                      start_time = start_time,
                      end_time = end_time)
#> Loading required namespace: geodist
#> Loading required namespace: lwgeom
#> Registered S3 method overwritten by 'spatstat':
#>   method     from
#>   print.boxx cli 
#> Linking to GEOS 3.8.1, GDAL 3.1.1, PROJ 6.3.1
if (FALSE) {
plot (ic)
}