Error: isTRUE(gpclibPermitStatus()) is not TRUE

Question

This question may be a duplicate of an earlier unanswered one. I still have the problem.

I am trying to use a zipcode shapefile and coming up with the following erro

Answer 1

You can look at Hadley's master file for ggplot2/R/fortify-spatial.r. Based on this outside link, my understanding is that lines 31–34 (in it's current form) used to read something like

# Union together all polygons that make up a region
try_require(c("gpclib", "maptools"))
unioned <- unionSpatialPolygons(cp, invert(polys))

So back then one way to attack the problem was to turn on the license

library(rgdal)
library(maptools)
if (!require(gpclib)) install.packages("gpclib", type="source")
gpclibPermit()

As @rcs, @Edzer Pebesma, and this answer mention, rgeos should resolve the issue for more recent installations.