Personal ggplot tips and tweaks
I love making plots in R with
ggplot. However, there are always a few niggles that I forget about between plots. I wrote this post so that I have somewhere to look the next time I need to tweak a few things in my plots. I intend to come back and add updates in the future as I learn more things. If I keep coming back, I might also remember a few of these too.
I’m always getting caught out by labels. How the heck do I change such and such to a larger font and so on? For most things the
theme() function comes to my rescue. It’s just a matter of remembering all the elements that can be altered. There are so many that there’s no shame in forgetting a few. Thankfully the documentation for
ggplot is great and it’s easy to find the relevant setting. It’s worth bearing in mind that there are additional helper functions that do things in
ggplot. For example, in the code:
ggplot(DF, aes(x=my_bars)) + geom_bar() + theme_minimal() + xlab("My x axis") + ylab("My y axis") + theme( axis.text = element_text(size = 16), axis.title = element_text(size = 16))
axis.text refers to the axis labels and
axis.title to the axis titles. The
ggplot to alter the text. Here we set the size to 16pt but you can also alter the font, the weight, the colour and so on. Another such helper function is
element_rect() to which you can pass properties you want for the background rectangle. See further down this post for an example.
One more source of help is
cookbook-r.com, which has lots of practical advice, particularly for all those fiddly legend alterations and custom colourings.
Look and feel.
Quite a few themes have popped up in recent years as
ggplot has become almost the default form of R graphics. It’s not essential but I thought I’d share a few of my favourites. From the themes that come with vanilla
tidyverse, my favourite is
theme_minimal() even if it is a little dour.
Because of this blog’s current theme I am often using the
ggthemes package, in particular
theme_tufte() to match with my jekyll theme. However, I do need to use one of a couple of tricks if I want to use the figures on this blog. One way is to alter the colour of the background to match this site. The other is a transparency trick that I’ll point out later on.
This week I also came across the
hrbrthemes package, which also has a neat style using Google’s ubiquitous Roboto Sans font. As an added bonus the package also includes a spellchecker that makes sure you’ve spelt your titles and labels correctly. Check out the examples, they look pretty smart.
Other fun theme packages worth investigating include
gg_sci (themes based on science journals and science fiction shows) and
gg_tech (themes based on tech companies such as Airbnb). The latter package’s Twitter theme fits well with the colour scheme of the council’s official slide deck so I might use it at work in future.
Exporting transparent graphics.
I think that exporting graphs with coloured backgrounds to match this website is a reasonable workaround but the best approach is to export
png files with transparent backgrounds. A quick search of stackoverflow brings up the following commands:
p <- p + theme( # bg of the panel rect = element_rect(fill = "transparent") ) p ggsave(p, filename = "tr_tst2.png", bg = "transparent")
p is a previously created
ggplot. This approach sees the
theme() function ride to the rescue again.