R (markdown) code to overlay lat/longs on a static map with OSM base.

Display_LatLon_OSM.R

library("ggmap")
library("mapproj")

### Tunisia Map
``` {r Map, dpi=100,echo=FALSE, message=FALSE, comment=NA, fig.width=6}


# get map image from google
map <- get_map(location = c(lon = 9.489765, lat = 35.584840), source = "osm", zoom = 6)

# start a ggplot. it won't plot til we type p
p <- ggmap(map)

# add points last so they are on top
p <- p + geom_point(data=data,aes(x=lon, y=lat),colour="red",size=4, na.rm = TRUE) + theme ( 
  	panel.grid.major = element_blank (), # remove major grid
		panel.grid.minor = element_blank (),  # remove minor grid
		axis.text = element_blank (), 
		axis.title = element_blank (),
		axis.ticks = element_blank ()
		) 

# display plot
p

#HT http://stackoverflow.com/questions/14095495/ploting-coordinates-of-multiple-points-at-google-map-in-r
```