[R-sig-Geo] subsetting a spatial polygons

[Tim Appelhans]

Antonio,

I am not sure why you think that your solution is not very elegant.
In case you want to have more visual control over the subsetting, you 
could try mapedit:

library(mapedit)
myselection = selectFeatures(polys, mode = "draw")

which will let you draw a e.g. rectangle and only return those features 
that intersect it.

Best
Tim


On 09/12/2018 04:18 AM, Antonio Silva wrote:
> Dear list users
>
> I have a SpatialPolygons with several squares. How to subset it to have
> only the squares between given latitudes and longitudes?
>
> In the example
>
> library(sp)
> library(raster)
> grd <-
> GridTopology(cellcentre.offset=c(-47.75,-25.416667),cellsize=c(10/60,10/60),cells.dim=c(23,12))
> polys <- as.SpatialPolygons.GridTopology(grd)
> proj4string(polys) <- CRS("+proj=longlat +datum=WGS84")
> plot(polys,axes=T)
>
> How to select only the squares, let's say, between 24-25°S and 45-46°W?
>
> The farthest I went was:
>
> e <- extent(-45.9,-45.1,-24.9,-24.1) # which is not very elegant
> mask <- crop(polys,e)
> polys2 <- polys[mask,]
> plot(polys2,add=T,col="green")
>
> Thanks a lot. Best regards
>