Local distribution maps for biological records in R

I thought it worth sharing this map that I created for a poster that Ambroise Baker and myself have prepared for the upcoming BSBI Annual Exhibition Meeting. It shows the occurrences of the non-native grass Polypogon viridis in Sheffield, based on records made by Ambroise and myself this year (2013). The map took a fair bit of fiddling around; working out how to correctly specify the manual scaling of the points seemed to cause me particular trouble!

Of course, R could also be used to create more traditional atlas dot maps; coastal outlines of Britain are freely available in more than one R package, and occurrence data relating to the UK grid could be manipulated in R to centre on monads, tetrads or hectads. External tools could also be used to do this before loading the data into R, e.g. see here.


The result is below. I'd be grateful to hear from anyone who can suggest any refinements to my code, or the general way in which I've gone about this.

Polypogon viridis in Sheffield, UK, 2013