In one of my previous blog post, I used the facet_wrap function in ggplot2 package to build a grid facet to display the rank history of each Eurovision competition country.
The grid facet looks pretty neat as all sub-panels are perfectly aligned, however, it fails to display the geospatial information of the countries that may reveal some useful insights. For example, in my last blog post , I built a voting network chart of Eurovision competition that has revealed the mutual high voting scores between some neighbour countries.
There is a R package, namely geofacet, which comes with a list of pre-built geospatial grids for a number of geographical areas, countries and states. One of the pre-built grids is for Europe area which is perfect for our Eurovision example.
It is very straightforward to use the geofacet package. After referenced the package in our R script, all we need to do is to replace the facet_wrap function in our ggplot2 code with the facet_geo function provided by the geofacet package. We need to specify the column by which the facet is divided and the name of the pre-built grid we will use. In this example, we use “eu_grid1” which is the grid for Europe area.
Now we have done all the work to convert our standard grid facet to geospatial facet. You can download the pbix file here.
Apart from the Europe area grid, you can find a list of other pre-built grids here. Considering where I am living at this moment, another pre-built grid I am particularly interested at is the London Borough grid. This is a geo-facet chart I have created to visualise the unemployment rate in the London boroughs.
You can also create your own grid which is literally a data frame with four columns, name and code columns that map to the facet label column in the dataset, and the row and col columns that specify the grid locations.
This is a test grid I have created to demonstrate how to create custom grid:
customGrid <- data.frame( name = c("Enfield", "Haringey", "Islington", "Hackney", "Camden", "Hackeny", "Redbridge", "Brent", "Ealing"), code = c("Enfield", "Haringey", "Islington", "Hackney", "Camden", "Hackeny", "Redbridge", "Brent", "Ealing"), row = c(1, 2, 3, 3, 3, 3, 3, 4, 5), col = c(3, 3, 5, 4, 1, 2, 3, 3, 3), stringsAsFactors = FALSE )