Overlapping calendar checker

[higgicd]

Good morning @dhersz, @rafapereirabr, et al., I developed a little function for our book that checks GTFS calendars to see if they overlap. You can see the code and the function working here. It reads all the GTFS files in a folder and creates an overlapping Gantt-style plot and an overlapping service days calendar - great for the case of multiple GTFS feeds.

Not sure if we will be packaging custom functions with our book but @rafapereirabr suggested this could be a good fit for {gtfstools}. It would have to be turned into a proper package function though.

(oof I had the wrong link in my post, pasted the rendered local quarto page 😵 updated now!)

[rafapereirabr]

Thank you for opening this issue, Chris ! I think this would be a great addition to the package. I can have a go in tying to create a first version of the function integrated into {gtfstools}.
A question I have related to UI, though, is whether the input of the function should be a list with the paths to gtfs.zip files, or whether it shoud be a list with gtfs files in memory with class "dt_gtfs" "gtfs" "list" , making sure the user has already used gtfstools::read_gtfs()

[higgicd]

Your call - my take is when running an accessibility analysis, the calendar is critical when you have >1 GTFS feed - therefore just being able to check that aspect in one step is quick and nice. If I had to read in all my GTFS feeds first, then call the calendar checker on them, that is potentially many steps for the average user. Could the input be both? If a folder, it wraps read_gtfs() as it currently behaves, or a list of gtfstools objects?