Convert {sf} geometry to Rust native primitives

sfconversions

A minimal Rust library to convert geometry objects from the R package {sf} into geo-types geometry primitives using extendr.

Provides simple conversions between sfg, sfc objects from sf, and geometry primitives from geo_types that can be used with other georust libraries powered by extendr.

Due to the orphan rule conversion directly from extendr Lists to geo_types is not possible. For that reason a simple struct Geom is implemented with a single field geom which contains a geo_types Geometry enum.

Example

Basic conversion from sfg objects is done with sfg_to_geo().

use sfconversions::{sfg_to_geometry, geom::Geom};

#[extendr]
fn sfg_to_geo(x: Robj) -> Geom {
    // takes a single `Robj` and converts it to `Geom`.
    // if the appropriate Robj class isn't found
    // a single point with coords (0, 0) is returned
    let geo = sfg_to_geometry(x);
    // extract the Geometry
    geo.geom
}

The Geom struct implement From<Geom> for Robj so converting from a Geom to the corresponding sfg object is fairly straight forward. Further, the From trait is also implemented for Geometry enums.

sfconversions acts similarly to sfheaders in that it returns the correct R objects with the appropriate classes without dependence upon sf. If sf is not available the conversions still will work but the print methods and other functions from sf will not be available.

From<Geom> also applies the appropriate sfg classes making direct conversion to sf fairly straight forward. Note that there is no concept of a CRS in geo_type so that information will be dropped.

Additionally, there is no conversion to sfc objects at this moment. To create an sfc object return a List of sfg objects and in R use sf::st_sfc() to complete the conversion.

See examples in h3o for conversion.