Adjust the speeds of a gps-like table created with gtfs2gps

Source: R/adjust_speed.R

Some GTFS.zip data sets might have quality issues, for example by assuming that a trip speed is unreasonably high (e.g. an urban bus running over 100 Km/h), or in other cases the `timestamp` information might be missing for some route segments. This can lead a gps-like table to have `NA` or unrealistic `speed` and `timestamp` values. This function allows the user to adjust the speed of trips and updates `timestamp` values accordingly. The user can adjust the problematic speeds by either setting a custom constant value, or by considering the average of all valid trips speed (Default). The columns `timestamp` and `cumtime` are updated accordingly.

adjust_speed(
  gps_data,
  min_speed = 2,
  max_speed = 80,
  new_speed = NULL,
  clone = TRUE
)

Arguments

gps_data

A GPS-like data.table created with gtfs2gps.

min_speed

Minimum speed to be considered as valid. It can be a numeric (in km/h) or a units value able to be converted to km/h. Values below minimum speed will be adjusted. Defaults to 2 km/h.

max_speed

Maximum speed to be considered as valid. It can be a numeric (in km/h) or a units value able to be converted to km/h. Values above maximum speed will be adjusted. Defaults to 80 km/h.

new_speed

Speed to replace missing values as well as values outside min_speed and max_speed range. It can be a numeric (in km/h) or a units value able to be converted to km/h. By default, `new_speed = NULL` and the function considers the average speed of the entire gps data.

clone

Use a copy of the gps_data? Defaults to TRUE.

Value

A GPS-like data with adjusted `speed` values. The columns `timestamp` and `cumtime` are also updated accordingly.

Examples

library(magrittr)
poa <- read_gtfs(system.file("extdata/poa.zip", package="gtfs2gps")) %>%
  gtfstools::filter_by_shape_id("T2-1") %>%
  gtfstools::filter_by_weekday(c("monday", "wednesday")) %>%
  filter_single_trip()
#> Unzipped the following files to /tmp/Rtmp8QhZHv/gtfsio:
#>   * agency.txt
#>   * calendar.txt
#>   * routes.txt
#>   * shapes.txt
#>   * stop_times.txt
#>   * stops.txt
#>   * trips.txt
#> Reading agency.txt
#> Reading calendar.txt
#> Reading routes.txt
#> Reading shapes.txt
#> Reading stop_times.txt
#> Reading stops.txt
#> Reading trips.txt

poa_gps <- gtfs2gps(poa)
#> Converting shapes to sf objects
#> Using 1 CPU cores
#> Processing the data
#> 
#> Attaching package: ‘purrr’
#> The following object is masked from ‘package:magrittr’:
#> 
#>     set_names
#> 
#> Attaching package: ‘data.table’
#> The following object is masked from ‘package:purrr’:
#> 
#>     transpose
#> Linking to GEOS 3.6.2, GDAL 2.2.3, PROJ 4.9.3; sf_use_s2() is TRUE
#> udunits database from /usr/share/xml/udunits/udunits2.xml
#> Some 'speed' values are NA in the returned data.
poa_gps_new <- adjust_speed(poa_gps)