title: plotting SpatialPointsDataFrame over a SpatialPolygonsDataFrame
body: <p>I have a SpatialPolygonsDataFrame that I plot using the following command:</p>
  
  <pre><code>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 ")
  </code></pre>
  
  <p>I have created a spatialPointsDataFrame with the following command </p>
  
  <pre><code>agenziePoints&lt;-SpatialPointsDataFrame(coords=datiAgenzie[,c("Long","Lat")],data=datiAgenzie,proj4string = llCRS, match.ID = TRUE).
  </code></pre>
  
  <p>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.</p>