points_on_polygons.R

library(sp)
library(maptools)

# get North Carolina shape data
NC <- readShapePoly(system.file("shapes/sids.shp", package = "maptools")[1],
          IDvar = "FIPSNO", proj4string = CRS("+proj=longlat +ellps=clrk66"))

# plot polygons
plot(NC, border = "blue", axes = TRUE, las = 1)

# create random spatial points object
set.seed(123)
points <- spsample(x = NC, n = 100, type = "random")

# promote to SpatialPointsDataFrame
points_df <- SpatialPointsDataFrame(points, data = data.frame(point_id = 1:100))

# add points to plot
plot(points_df, col = "orange", add = TRUE)