Barchart: italics in legend

Question

I'm trying to keep the first label in the legend plain whilst converting the rest into italics, but I don't know how to do this. The code I'm using is:

ggplot(the_data_mod) +
  geom_bar(aes(x = Protein, y = Protein_Abundance, fill = Mutant), 
           stat = "identity", position = position_dodge(), col = "white") + 
  theme_minimal()+   
  labs(title = "Relative Levels of TOC Protein Abundance across SP2 Mutants", 
       x = "Protein")+
  ylab(expression(atop("Protein Abundance", paste("(Normalised Relative to WT)"))))

and the data is:

structure(list(Mutant = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L), .Label = c("WT", "ppi1", "sp2-4", "sp2-1 ppi1", "sp2-3 ppi1", "sp2-5 ppi1", "sp2-6 ppi1", "sp2-8 ppi1"), class = "factor"), Protein = c("TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159" ), Protein_Abundance = c(100, 19.79, 209.85, 364.6, 183.14, 435.02, 22.23, 109.79, 100, 39.52, 266.72, 88.66, 105.04, 132.01, 99.7, 140.1349751)), class = "data.frame", row.names = c(NA, -16L))

Could you possibly use `dput(the_data_mod)` and post the output please? It's very difficult to read in your sample data — tjebo, Jan 02 '20 at 11:30
structure(list(Mutant = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L), .Label = c("WT", "ppi1", "sp2-4", "sp2-1 ppi1", "sp2-3 ppi1", "sp2-5 ppi1", "sp2-6 ppi1", "sp2-8 ppi1"), class = "factor"), Protein = c("TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC75", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159", "TOC159" ), Protein_Abundance = c(100, 19.79, 209.85, 364.6, 183.14, 435.02, 22.23, 109.79, 100, 39.52, 266.72, 88.66, 105.04, 132.01, 99.7, 140.1349751)), class = "data.frame", row.names = c(NA, -16L)) — Tanya, Jan 02 '20 at 12:15
You have asked [a very similar question here](https://stackoverflow.com/questions/59554096/ggplot2-italics-in-the-legend) It would be generally appreciated if you would point to previous questions of similar (in this case: the same!) gist, so that the people who help you have it easier — tjebo, Jan 02 '20 at 16:06

UseR10085 · Accepted Answer · 2020-01-02T11:51:06.013

You can use the following code for that

  ggplot(the_data_mod, aes(x = Protein, y = Protein_Abundance, fill = Mutant)) + 
  geom_bar(stat = "identity", position = position_dodge(), col = "white") +
  scale_fill_discrete("Mutant",
                      labels = c(expression(italic("ppi1")), 
                                 expression(italic("sp2-1 ppi1")),
                                 expression(italic("sp2-3 ppi1")),
                                 expression(italic("sp2-4")),
                                 expression(italic("sp2-5 ppi1")), 
                                 expression(italic("sp2-6 ppi1")),
                                 expression(italic("sp2-8 ppi1")),
                                 expression(italic("WT")))) + 
  theme_minimal()+  
  theme(legend.text.align = 0)+  
  labs(title = "Relative Levels of TOC Protein Abundance across SP2 Mutants", 
       x = "Protein")+
  ylab(expression(atop("Protein Abundance", paste("(Normalised Relative to WT)"))))

[here is a function which helps avoid typing out all those expressions](https://stackoverflow.com/a/44661732/7941188). — tjebo, Jan 02 '20 at 13:28

tjebo · Answer 2 · 2020-01-02T14:32:06.657

If your aim is to italicise all your legend labels, you can simply use theme.
If you have several legends and only want to italicise one of them, you can specify this with the guide argument in your scale calls (see below, Credit to @Henrik 's answer here)
If you only want to italicise certain categories, either use @BappaDas option or use @MrFlicks function from here (you can tweak the ifelse statement within the function)

library(tidyverse)

# Easiest option

ggplot(the_data_mod) +
  geom_bar(aes(x = Protein, y = Protein_Abundance, fill = Mutant), 
           stat = "identity", position = position_dodge(), col = "white") + 
  theme(legend.text = element_text(face = "italic"))

# or (for the case of several legends)

ggplot(the_data_mod) +
  geom_bar(aes(x = Protein, y = Protein_Abundance, fill = Mutant), 
           stat = "identity", position = position_dodge(), col = "white") + 
  scale_fill_discrete(guide = guide_legend(label.theme = element_text(angle = 0, face = "italic")))

^{Created on 2020-01-02 by the reprex package (v0.3.0)}

Barchart: italics in legend

2 Answers2