Gabriela D'Souza 22/11/2018
To create geographical flows of data using waste plastics exports as an example
Packages used for this project include * tidyverse * sf * what else? * gganimate
We were interested in creating a better interface for the mapping flows of trade and other variable data across geographical boundaries.
Our first step was to create a package that would allows users to build visualisations of flows between geographical destinations which in our example was countries.
We subsequently found Joshua Kunst's geom_curve which rather helpfully allows us to specify curves between locations. This made our project much easier, as we had initially thought we might have to create our own package to do this.
We initially thought that we could just use geom_curve however we realised that geom_curve doesn't do a great circle, it's just a way of connecting an x and y point and therefore was not suitable for mapping. While this might work on detailed maps using just a handful of countries, or one country, it doesn't work on a global scale so we had to scrap this idea.
Simplefeatures was better geared towards mapping and contains geographical objects that respond to correct mapping (as long as you don't include the problematic north and south pole (see more below)).
We encountered a problem with specifying the direction of flows. While geom_curve allowed us to have arrows on our lines, the simple features suite of functions wouldn't. So we experimented t geom_sf unfortunately does not allow us to specify arrows on our flows
Workaround using Line objects to work with great circles or straightlines to work between two sets of points, but involves manipulating the lines representing flows to shorten them at the ends, which can be achieved by buffering locations and intersecting the points with the lines (all part of sf functionality).
