How to intersect lines and polygons in R?

Question

Following on from an answer about intersecting polygons with lines to chop up a polygon into smaller polygon units (in QGIS), I wanted to try the same thing in R. However, I cannot seem to find a method that works!

over() doesn't have a method for polygons intersecting with lines; I found gIntersection() from rgeos but it fails:

require(sp)
require(rgeos)

poly <- readShapePoly("polygon.shp")
lines <- readShapeLines("lines.shp")

chopped <- gIntersection(poly, lines)

Giving:

Error in RGEOSBinTopoFunc(spgeom1, spgeom2, byid, id, "rgeos_intersection") : 
  UnsupportedOperationException: GeometryGraph::add(Geometry *): unknown geometry type: N4geos4geom18GeometryCollectionE

Update: Here's a link to the files in question.

Update 2: PaulG notes that it works and after updating rgeos and R I got rid of the error above. Thanks PaulG ...

However, gIntersection results in a SpatialLines object no matter whether I put in (poly, lines) or (lines, poly) - whereas the operation I did in QGIS (or Arc, back in the bad ol' days) will divide a polygon with the lines and result in a polygon object, not line.

So, how do I chop up my polygon with the lines and get polygons out?

Answer 1

You could try using RSAGA. I'm not too familiar with it myself, but the command would be something like:

rsaga.geoprocessor("libshapes_polygons", "Polygon-Line Intersection", list(POLYGONS="polygonshape.shp",LINES="lineshape.shp",INTERSECT="result.shp"))

Answer 2

I've been facing the same problem several times. I'will focus on two methods that works for me

1) The intersect function from raster package. It returns a SpatialLinesDataframe including the id of each polygon.

library(raster)
newLines <- raster::intersect(SpatialLinesDataframe, SpatialPolygonDataframe)

2) Calling QGIS from R with the package RQGIS, as showed here I think that this method is faster than several other, but you have to take care with the qgis version. Here is the github of the creator. Also, with this package you can use any of the geoalgoritm from qgis.

library(RQGIS)    
qgis_env <- set_env("PATH")
params <- get_args_man(alg = "qgis:intersection", 
                           qgis_env = qgis_env)
params$INPUT <- line_1
params$INPUT2 <- poly_1
out <- run_qgis(alg = "qgis:intersection",
                params = params,
                load_output = params$OUTPUT,
                qgis_env = qgis_env)

EDIT in 2018: I was thinking and you polygon with another polygon, to get smaller polygons: Take a look of this link for the Manual of the new sf R package (Pebesma, 2018).

• Edzer Pebesma (2018). sf: Simple Features for R. R package version 0.6-3. https://CRAN.R-project.org/package=sf
• Pebesma, E., 2018. Simple Features for R: Standardized Support for Spatial1995 Vector Data. The R Journal.