Hello, I was getting the same error mentioned in #346 specifically:
`Error in `dplyr::summarise()`:
ℹ In argument: `polygons = `%>%`(...)`.
Caused by error:
! TypeError: Cannot read properties of undefined (reading '0')`
I discovered that more generally this error appears if your nearest network vertex is not within the travel-time+mode combination specified which can be quite common in more rural areas. For example, if your travel time is relatively low (e.g. 5-minutes) and your only estimating walking. I thought I would flag this as a "bug" (but its more of a feature of how the isochrones are calculated) and perhaps it could be documented somewhere. Also if there are many start points (some that do have multiple vertices in the correct distance) it prevents isochrones being generated for any of them, and its not clear from the error which start point "broke" the function.
It may be outside of the scope of the package, but could there be an option to calculate simple (but probably more computationally expensive) line isochrones (following the road network rather than providing a polygon), these could be perhaps limited to low road/footpath density contexts and considering distances less than 1 km? Maybe another option where below a certain vertex density there is some additional sampling done along the polylines to calculate a bigger distance matrix?
There are also generally more distortions as well in low-road density contexts with isochrones only covering perhaps a small fraction of the only accessible road. Low-road density can be quite common in more isolated rural areas where nodes along country roads maybe much further than a five or 10 minute walk away.
Below is an example area.
Thanks for your efforts!
house <- st_sfc(st_point(c(-2.24415, 57.11189)),crs=4326)
ruralarea <- st_as_sfc(st_bbox(c(xmin = -2.239323, xmax = -2.249966, ymax = 57.114902, ymin = 57.109682), crs = st_crs(4326)))
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