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Derive a stops table from supplied route geometries

Source: R/geometry_import.R
g2g_stops_from_geometries.Rd

Builds the stops_data input for g2g_extract_trips_and_stop_times from the route's own linestrings and a plain table of stop coordinates, with no GTFS feed involved: a stop belongs to a direction when it lies within buffer_m of that direction's line.

Usage

g2g_stops_from_geometries(geometries, stops, route_id, buffer_m = 50)

Arguments

geometries

The route geometries, in either of two forms:

  • a data.frame of vertices in long form, with columns route_id, direction, vertex_seq (the numeric order of the vertices within a direction), latitude and longitude; or

  • an sf object of LINESTRING or MULTILINESTRING geometries with route_id and direction columns (requires the 'sf' package). MULTILINESTRING parts are concatenated in part order.

stops

A data.frame of stop coordinates with columns stop_id, latitude, longitude. Any other columns are dropped. Rows with a missing coordinate, or a missing or blank stop_id, are dropped with a warning giving the counts.

route_id

A single route identifier present in geometries. The gps2gtfs pipeline models one route (two terminals) at a time.

buffer_m

Numeric. Maximum distance in meters from a direction's line for a stop to be assigned to that direction. Default 50.

Value

A data.table with columns stop_id, latitude, longitude, direction (the terminal_id of the direction the stop was matched to), sorted by direction then stop_id. Stops matched in both directions appear once per direction. Zero rows, with the same four columns and types, when no stop is within buffer_m of either direction.

Details

Distance is measured to the polyline, not to its vertices. A stop sitting halfway along a 300 m segment is on the route; a nearest-vertex rule would measure 150 m and drop it.

Direction labels are the terminal_ids that g2g_terminals_from_geometries emits for the same input, so the two tables drop into terminals_data and stops_data together and no stop_direction_map is needed.

A stop within buffer_m of both lines - the usual case for the two sides of one street - is returned once per direction, which is what makes the direction labels do any work. Stops farther than buffer_m from every direction are simply absent, and their count is reported in a message. If that is every stop, the result is a zero-row table and a warning, not an error, so a caller looping over many routes can take that answer for one of them. Terminals are not treated specially and are not removed.

See also

g2g_terminals_from_geometries for the matching terminals_data, and g2g_stops_from_gtfs for the same table derived from a planned GTFS feed.

Examples

geometries <- data.frame(
  route_id = "r1",
  direction = rep(c("east", "west"), each = 3),
  vertex_seq = rep(1:3, times = 2),
  latitude = c(7.29, 7.30, 7.31, 7.31, 7.30, 7.29),
  longitude = c(80.63, 80.64, 80.65, 80.65, 80.64, 80.63)
)
stops <- data.frame(
  stop_id = c("S1", "S2"),
  latitude = c(7.295, 7.305),
  longitude = c(80.635, 80.645)
)
g2g_stops_from_geometries(geometries, stops, route_id = "r1")
#> Key: <direction, stop_id>
#>    stop_id latitude longitude direction
#>     <char>    <num>     <num>    <char>
#> 1:      S1    7.295    80.635      east
#> 2:      S2    7.305    80.645      east
#> 3:      S1    7.295    80.635      west
#> 4:      S2    7.305    80.645      west