Converting a “map” object to a “SpatialPolygon” object

Question

I am guessing there is a simple solution to the problem I have been having, but I am having some trouble.

I am trying to convert the following map objec

Answer 1

Polygons have surface (area), therefore the key argument is fill = TRUE in

usa <- map('state', fill = TRUE)

Changing the argument value to TRUE stops the error message.

Answer 2

Just found some code in the text "Applied Spatial Data Analysis with R". It works great!

require(maps)
usa <- map("state", fill = TRUE)

require(sp)
require(maptools)
IDs <- sapply(strsplit(usa$names, ":"), function(x) x[1])
usa <- map2SpatialPolygons(usa, IDs=IDs, proj4string=CRS("+proj=longlat +datum=WGS84"))