How to use greek characters in ggplot2?

Question

My categories should be named in Greek letters. I use ggplot2 and it works great with data. Unfortunately, I cannot figure out how to put these Greek characters on the x axis (at the marks), and also make them appear in the legend. Is there any way to do this?

UPDATE: I looked at the link, however there is no good method described to accomplish what I want to do.

Answer 1

Here is a link to an excellent wiki that explains how to put Greek characters in ggplot2. So here is what you do to get Greek characters

• Text labels: Use parse = T inside geom_text or annotate .
• Signs of the axes: Use expression(alpha) to get Greek alpha.
• Granite labels: Use labeller = label_parsed inside facet .
• Legend legend: Use bquote(alpha == .(value)) in the legend label.

You can see the detailed use of these parameters in the link.

EDIT. The purpose of using Greek characters along labels can be achieved as follows

 require(ggplot2); data(tips); p0 = qplot(sex, data = tips, geom = 'bar'); p1 = p0 + scale_x_discrete(labels = c('Female' = expression(alpha), 'Male' = expression(beta))); print(p1); 

For complete documentation of the various symbols that are available for this and how to use them, see ?plotmath .

Answer 2

Use expression(delta) where 'delta' for lowercase δ and 'Delta' for capital Δ .

Here is a complete list of Greek characters:

A α alpha
Β β beta
Γ γ gamma
Δ δ delta
E ε epsilon
Ζ ζ zeta
Η η eta
Θ θ theta
Ι ι iota
Κ κ kappa
Λ λ lambda
Μ μ mu
Ν ν nu
Ξ ξ xi
Ο oh omicron
Π π pi
Ρ ρ rho
Σ σ sigma
Τ τ tau
Υ υ upsilon
Φ φ phi
Χ χ chi
Ψ ψ psi
Ω ω omega

EDIT: Copied from comments, when used in combination with other words, use: expression(Delta*"price")

Answer 3

The easiest solution: use Unicode characters

expression or other packages are not needed.
Not sure if this is a newer feature for ggplot, but it works. It also makes it easy to mix Greek and plain text (for example, adding '*' to checkmarks)

Just use Unicode characters in the text string. It seems to work well for all the options I can come up with. Edit: previously it did not work in facet labels. This seems to have been fixed at some point.

 library(ggplot2) ggplot(mtcars, aes(mpg, disp, color=factor(gear))) + geom_point() + labs(title="Title (\u03b1 \u03a9)", # works fine x= "\u03b1 \u03a9 x-axis title", # works fine y= "\u03b1 \u03a9 y-axis title", # works fine color="\u03b1 \u03a9 Groups:") + # works fine scale_x_continuous(breaks = seq(10, 35, 5), labels = paste0(seq(10, 35, 5), "\u03a9*")) + # works fine; to label the ticks ggrepel::geom_text_repel(aes(label = paste(rownames(mtcars), "\u03a9*")), size =3) + # works fine facet_grid(~paste0(gear, " Gears \u03a9")) 

^{Created on 2019-08-28 by the reprex package (v0.3.0)}

Answer 4

You do not need the latex2exp package to do what you want to do. The following code could do the trick.

 ggplot(smr, aes(Fuel.Rate, Eng.Speed.Ave., color=Eng.Speed.Max.)) + geom_point() + labs(title=expression("Fuel Efficiency"~(alpha*Omega)), color=expression(alpha*Omega), x=expression(Delta~price)) 

In addition, some comments (unanswered at the moment) asked to put an asterisk (*) after the Greek letter. expression(alpha~"*") works, so I suggest trying.

More comments were asked about getting Δ Price and I find the easiest way to achieve this expression(Delta~price)) . If you need to add something before the Greek letter, you can also do this: expression(Indicative~Delta~price) which gets you: