plotting SpatialPointsDataFrame over a SpatialPolygonsDataFrame

Question

I have a SpatialPolygonsDataFrame that I plot using the following command:

spplot(milanoNILNew, "percPolVita",at = c(0,0.0696,0.08979,0.0974,0.1116,0.181),col.regions =pal,main="Quota Clienti Unipol con Polizze Vita ")

I have created a spatialPointsDataFrame with the following command

agenziePoints<-SpatialPointsDataFrame(coords=datiAgenzie[,c("Long","Lat")],data=datiAgenzie,proj4string = llCRS, match.ID = TRUE).

I'm able to plot the polygons but I am not able to represent agenziePoints on the polygons on the same plot. Thanks in advance for the support.

Schmit

Answer 1

Just use the base plot function with the add=TRUE argument.

require(sp)

# Create polygons
sr=SpatialPolygons(list(
  Polygons(list(Polygon(cbind(c(180114,180553,181127,181477,181294,181007,180409, 
  180162,180114),c(332349, 332057, 332342, 333250, 333558, 333676, 332618, 332413, 332349)))),"1"),
  Polygons(list(Polygon(cbind(c(180042,180545,180553,180314,179955,179142,179437,179524,179979,180042), 
  c(332373,332026,331426,330889,330683,331133,331623,332152,332357,332373)))),"2")))
srdf=SpatialPolygonsDataFrame(sr, data.frame(cbind(1:2,1:2), row.names=c("1","2")))

# Add points (sp meuse dataset)
data(meuse)
coordinates(meuse) = ~x+y

# Create a color vector for the meuse points
color <- rep("xx", nrow(meuse@data))
  color[(meuse@data$copper > 0)&(meuse@data$copper <= 31)] <- "black"
    color[(meuse@data$copper  > 31)] <- "red"

# Plot polygons with points overlaid    
plot(srdf, col=c("grey","blue"))
  plot(meuse, col=color, pch=19, add=TRUE) 

If you really want to use the spplot function you could implements something like this:

# spplot approach
pts=list("sp.points", meuse, pch=19, col=color)
  spplot(srdf, "X1", col.regions=c("grey","blue"), colorkey=FALSE,
         sp.layout=list(pts)) 

Picro