Convert frequencies to stop times — frequencies_to_stop

Creates stop_times entries based on the frequencies specified in the frequencies table.

Usage

frequencies_to_stop_times(gtfs, trip_id = NULL, force = FALSE)

Arguments

gtfs: A GTFS object, as created by read_gtfs().
trip_id: A character vector including the trip_ids to have their frequencies converted to stop_times entries. If NULL (the default), the function converts all trips listed in the frequencies table.
force: Whether to convert trips specified in the frequencies table even if they are not described in stop_times (defaults to FALSE). When set to TRUE, these mismatched trip are removed from the frequencies table and their correspondent entries in trips are substituted by what would be their converted counterpart.

Value

A GTFS object with updated frequencies, stop_times and trips tables.

Details

A single trip described in a frequencies table may yield multiple trips after converting the GTFS. Let's say, for example, that the frequencies table describes a trip called "example_trip", that starts at 08:00 and stops at 09:00, with a 30 minutes headway.

In practice, that means that one trip will depart at 08:00, another at 08:30 and yet another at 09:00. frequencies_to_stop_times() appends a "_<n>" suffix to the newly created trips to differentiate each one of them (e.g. in this case, the new trips, described in the trips and stop_times tables, would be called "example_trip_1", "example_trip_2" and "example_trip_3").

Examples

data_path <- system.file("extdata/spo_gtfs.zip", package = "gtfstools")
gtfs <- read_gtfs(data_path)
trip <- "CPTM L07-0"

# converts all trips listed in the frequencies table
converted_gtfs <- frequencies_to_stop_times(gtfs)

# converts only the specified trip_id
converted_gtfs <- frequencies_to_stop_times(gtfs, trip)

# how the specified trip_id was described in the frequencies table
head(gtfs$frequencies[trip_id == trip])
#>       trip_id start_time end_time headway_secs
#>        <char>     <char>   <char>        <int>
#> 1: CPTM L07-0   04:00:00 04:59:00          720
#> 2: CPTM L07-0   05:00:00 05:59:00          360
#> 3: CPTM L07-0   06:00:00 06:59:00          360
#> 4: CPTM L07-0   07:00:00 07:59:00          360
#> 5: CPTM L07-0   08:00:00 08:59:00          360
#> 6: CPTM L07-0   09:00:00 09:59:00          480

# the first row of each equivalent stop_times entry in the converted gtfs
equivalent_stop_times <- converted_gtfs$stop_times[grepl(trip, trip_id)]
equivalent_stop_times[equivalent_stop_times[, .I[1], by = trip_id]$V1]
#>             trip_id arrival_time departure_time stop_id stop_sequence
#>              <char>       <char>         <char>  <char>         <int>
#>   1:   CPTM L07-0_1     04:00:00       04:00:00   18940             1
#>   2:   CPTM L07-0_2     04:12:00       04:12:00   18940             1
#>   3:   CPTM L07-0_3     04:24:00       04:24:00   18940             1
#>   4:   CPTM L07-0_4     04:36:00       04:36:00   18940             1
#>   5:   CPTM L07-0_5     04:48:00       04:48:00   18940             1
#>  ---                                                                 
#> 157: CPTM L07-0_157     23:00:00       23:00:00   18940             1
#> 158: CPTM L07-0_158     23:12:00       23:12:00   18940             1
#> 159: CPTM L07-0_159     23:24:00       23:24:00   18940             1
#> 160: CPTM L07-0_160     23:36:00       23:36:00   18940             1
#> 161: CPTM L07-0_161     23:48:00       23:48:00   18940             1