Intersect
It depends on the classes of the x and y what is returned.
If x is a Raster* object the extent of y is used, irrespective of the class of y, and a Raster* is returned. This is equivalent to crop.
If x is a Spatial* object, a new Spatial* object is returned. If x or y has a data.frame, these are also returned (after merging if necessary) as part of a Spatial*DataFrame, and this is how intersect is different from rgeos::gIntersection on which it depends.
Intersecting SpatialPoints* with SpatialPoints* uses the extent (bounding box) of y to get the intersection. Intersecting of SpatialPoints* and SpatialLines* is not supported because of numerical inaccuracies with that. You can use buffer, to create SpatialPoygons* from SpatialLines* and use that in intersect. Or try gIntersection.
## S4 method for signature 'Extent,ANY' intersect(x, y) ## S4 method for signature 'Raster,ANY' intersect(x, y) ## S4 method for signature 'SpatialPoints,ANY' intersect(x, y) ## S4 method for signature 'SpatialPolygons,SpatialPolygons' intersect(x, y) ## S4 method for signature 'SpatialPolygons,SpatialLines' intersect(x, y) ## S4 method for signature 'SpatialPolygons,SpatialPoints' intersect(x, y) ## S4 method for signature 'SpatialLines,SpatialPolygons' intersect(x, y) ## S4 method for signature 'SpatialLines,SpatialLines' intersect(x, y)
x |
Extent, Raster*, SpatialPolygons*, SpatialLines* or SpatialPoints* object |
y |
same as for |
if x is an Extent object: Extent
if x is a Raster* object: Raster*
if x is a SpatialPoints* object: SpatialPoints*
if x is a SpatialPolygons* object: SpatialPolygons*
if x is a SpatialLines* object and if y is a SpatialLines* object: SpatialPoints*
if x is a SpatialLines* object and if y is a SpatialPolygons* object: SpatialLines*
e1 <- extent(-10, 10, -20, 20)
e2 <- extent(0, 20, -40, 5)
intersect(e1, e2)
#SpatialPolygons
if (require(rgdal) & require(rgeos)) {
p <- shapefile(system.file("external/lux.shp", package="raster"))
b <- as(extent(6, 6.4, 49.75, 50), 'SpatialPolygons')
projection(b) <- projection(p)
i <- intersect(p, b)
plot(p)
plot(b, add=TRUE, col='red')
plot(i, add=TRUE, col='blue', lwd=2)
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