Scale bar and North arrow on a ggplot2 map using R

After some research on the Internet, I gave up trying to find an R function to add a scale bar and a North arrow on a map, using ggplot().
So, I would like to present you what I have come up with.

The idea is really basic : we create two polygons for the scale bar, we add some text above, and we draw an arrow. That’s it. The only tricky thing here, is the way to obtain the coordinates of each element. An easy solution is to use the gcDestination function, from the maptools package.


Visualizing densities of spatial processes

In the past few weeks, Arthur Chaprentier (@freakonometrics) and I have been working again on an article untitled “Visualizing spatial processes using Ripley’s correction: an application to bodily-injury car accident location“.  The revised version of our work is available here: http://hal.archives-ouvertes.fr/hal-00725090.

Please note that this post is related to Arthur’s: http://freakonometrics.hypotheses.org/7129


Montreal border

After reading a really nice post about geo-marked bike accidents (Mapping Bike Accidents in R), I wanted to reuse the map for something else. Unfortunately, the shapefile used to create it does not give the entire border, but an aggregation of borough instead.

So, after a couple hour looking on the web for a simpler SHP file, I gave up and finally decided to create it myself. To do so, I used the SHP file given on the Mapping Bike Accidents post.

Montreal as a Polygon