Convert Spatial Polygons Data Frame to OWIN

Question

I am new to R and a new to programming. I have a shapefile which I have imported into R and found that it is a Spatial Polygons Data Frame. I want to use the crossdist function in spatstat but before that I am attempting to convert this into owin and then class psp as that is how I have read to address this issue. My problem is that I am not sure how to convert my data to owin. Any help on how to address this would be greatly appreciated. Thanks.

Answer 1

A SpatialPolygons or SpatialPolygonsDataFrame object represents a list of several distinct spatial regions, e.g. states of the USA, while an owin object represents a single spatial region (possibly consisting of several disjoint pieces), e.g. Hawaii.

To convert a SpatialPolygonsDataFrame (say x) to a list of owin objects:

y <- as(x, "SpatialPolygons")
p <- slot(y, "polygons")
v <- lapply(p, function(z) { SpatialPolygons(list(z)) }
winlist <- lapply(v, as.owin)

The result winlist is a list, each entry of which is an 'owin' object representing one of the polygonal regions in x.

For further information see the spatstat vignette on shapefiles: start R, load the spatstat package, type vignette('shapefiles') and view the section on SpatialPolygonsDataFrame objects.

For more detailed information, see the book on spatstat.