Running examples in 'gtfs2gps-Ex.R' failed
The error most likely occurred in:

> ### Name: adjust_speed
> ### Title: Adjust the speeds of a gps-like table created with 'gtfs2gps'
> ### Aliases: adjust_speed
> 
> ### ** 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 D:\temp\RtmpuSxrMe/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 3.10.2, GDAL 3.4.1, PROJ 7.2.1; sf_use_s2() is TRUE
udunits database from D:/temp/Rtmp0E9HKG/RLIBS_147a431897675/units/share/udunits/udunits2.xml
Some internal bug occurred while processing gtfs data.
Please give us a feedback by creating a GitHub issue
(https://github.com/ipeaGIT/gtfs2gps/issues/new)
and attaching a subset of your data created from the
code below:
################################################
$message
[1] "geometries - Expecting an integer vector for indexing"

$call
NULL

$cppstack
NULL

ids <- c('T2-1')
data <- gtfstools::filter_by_shape_id(poa, ids)
gtfs2gps::write_gtfs(data, 'shapes_with_error.zip')
################################################
0 out of 1 shapes (0%) were properly processed.
0 out of 1 trips (0%) were properly processed.
Error in Ops.units(output$speed, units::set_units(0, "km/h")) : 
  both operands of the expression should be "units" objects
Calls: gtfs2gps -> unique -> which -> Ops.units
Execution halted