Dear all,
I have a dataframe with around 90k observations over an area including a continent (a raster object), and a variable of interest whose values I want to visualize on a map. I have used levelplot function from lattice package to visualize the data, and added a map of the continent to the plot as a layer (using a shapefile). So far, so good.
My area of interest is the continent itself, but my data covers a larger area (including the oceans around the continent). I would like to keep the whole map but mask the ocean around the continent (with a buffer of 100km) and keep the values only for the continent.
I would appreciate it if someone could help me achieve this.
Thank you in advance,
Sohrab