Convex Hull implementation?

[spiry34]

Dear maintainers,
I need some convex hull functionalities in order to improve the "mapi" package at a worldwide scale.
I noticed a s2convex_hull_query exists in s2 library but I can't find out exports to R.
I tried to understand how to link these functions but I'm somewhat ill at ease (euphemism!) with the implementation of the links between R and s2.
Do you plan to add this functionality in r-s2?
Otherwise I will try to, but I don't really know where to start... :-/
Many thanks for "un-flattening" the earth with this package, anyway :-)
Sylvain Piry

[paleolimbot]

You're right! It exists in s2 and we should export to R. I'm happy to do this for the next release; however, if you want to give it a shot, you could try:

• Adding the R function s2_convex_hull() to R/s2-transformers.R
• Adding the C++ function cpp_s2_convex_hull() to src/s2-transformers.cpp. It's the most similar to cpp_s2_rebuild() ( https://github.com/r-spatial/s2/blob/main/src/s2-transformers.cpp#L476-L501 ), except instead of calling the rebuild function you'll use the geog->ShapeIndex() to pass it to the convex hull query.

Cheers!

[spiry34]

OK, I give a try! Your hints are a candle in the dark :-)
Thanks!
S.