michaeldorman
nngeo is failing with some CRS due to lack of units
Hi, I found this to fail here, is also related to https://github.com/r-spatial/sf/issues/2299.
points <- sf::st_sfc(
sf::st_point(c(0, 1)),
sf::st_point(c(0, 2)),
crs = 'LOCAL_CS["planar", UNIT["METER",1]]'
)
points2 <- sf::st_sfc(
sf::st_point(c(0, 1)),
sf::st_point(c(0, 2)),
crs = 'LOCAL_CS["planar", UNIT["METER",1]]'
)
nngeo::st_nn(points, points2)
projected points
Error in if (!is.na(crs_units) & crs_units != "m") { :
argument is of length zero
Here the line: https://github.com/michaeldorman/nngeo/blob/fcfde8ee0d236494aad120e0b86b5b21d7a2c7b0/R/st_nn_pnt_proj.R#L61
For some reason, SF is not setting the units for this CRS, maybe is only setting the ones that have the shortcut of numeric value, like 4326 for WGS84.
Thx.
Hi, after check this on SF package, this issue is generated because nngeo is trying to read from proj4string:
https://github.com/michaeldorman/nngeo/blob/fcfde8ee0d236494aad120e0b86b5b21d7a2c7b0/R/st_nn_pnt_proj.R#L58
We can access to the params using sf::st_crs()$something, the point is that proj4string is replaced with WKT2, and that causes to new CRSs can not be read.
The solution is use directly the units from SF package, as described: https://github.com/r-spatial/sf/issues/2299#issuecomment-1863385408
That should fix this all above this, searching on the project, can't found any more causes where this can affect, if you know some case would be good to be fixed too.
Thx!
Thanks! The error is now solved in https://github.com/michaeldorman/nngeo/commit/91085c0851dc9dc1f7e2442bba847d23aa0149b1 (the case is treated as a unitless CRS)
Hi! sadly that does not fix the issue, this comes of what sf::st_crs()$units access to a PRoj4String parameter, the point there is that not all WKT2 has a Proj4String expression, so some WKT2 will not have a value there.
But you can use sf::st_crs()$ud_unit https://github.com/r-spatial/sf/issues/2299#issuecomment-1863182678 which always retrieve the unit from the CRS.
Think I got it, thanks. Will appreciate if you can please check again.
The CRS unit is extracted using sf::st_crs()$ud_unit.