Composite plots: grid.arrange

I really like composite plots, where there’s a top part that describes a phenomenon and a bottom part with a synthetic time view of the overall process.
I’ve recently discovered this beautiful representation of educational differentials by gender, by Sara Lopus and Margaret Frye, and the beauty of this dataviz is that it tells a story on its own. (Click on the link for the publication)

I have used a random generated data to reproduce the graph in ggplot and used grid.arrange from gridExtra package to bind grobs, the top and bottom components.

grid.arrange(top, bottom, heights=c(10,5), widths=c(20), padding=0)

I have saved the map as a .png file png package and used rasterGrob from package grid to create a raster image graphical object.

Screen Shot 2018-08-30 at 11.26.50

Quick way to add annotations to your ggplot graphs

Lately, some of the graphs I have been working on have “strange/erratic” values, so I thought to plot those values in a different color and rather than adding an extra legend line I have decided to add a note to explain the difference. Among the many options available, I have found a very quick and harmless way to add annotations to ggplot graphs. It uses the library “gridExtra”, which employs user-level functions that work with “grid” graphics and draw tables.

1.load ggplot2 library
library(ggplot2)
2. and save your graph as “my_graph”:
my_graph<- qplot(wt, mpg, data = mtcars)
3. load gridExtra and add the text to the graph. Note that x, hjust and vjust give the position of the text in the outer margins. If you want to annotate INSIDE the graph, use annotate:
library(gridExtra)
g <- arrangeGrob(p, sub = textGrob("I pledge my life and honor to the Night's Watch, \nfor this night and all the nights to come.", x=0, hjust=-0.1, vjust=0.1,gp = gpar(fontface = "italic", fontsize = 10)))

5. save the graph
ggsave("my_graph_with_note.pdf", g, width=5,height=5)

my_graph_with_note

 

 

 

 

 

here is the graph I have been working on:

MORAN_I_MAC