Multiple Fixed Lines for Text per Legend Label in ggplot2

Question

(This question expands on Multiple Lines for Text per Legend Label in ggplot2 .)

I need to include multiple lines of information in legend labels. These labels need to be broken into lines at fixes points, which is why the solution in the previous example doesn't work for me. I've tried using \n , but in the expression I'm using, I end up with an offset.

set.seed(10)
dat_sof<-tibble(x=seq(1:10))%>%
            mutate(y=x+rnorm(10))

leg_col<-c("S1"="blue", "S2"='black')
leg_lty<-c("S1"=1, "S2"=2)
leg_lab<-c(expression("S1:\n y = m1 x + b1\n"~ R^{2} ~ " = r1, n = n1"), 
           expression("S2:\n y = m2 x + b2\n"~ R^{2} ~ " = r2, n = n2"))

ggplot(data=dat_sof, aes(x=x, y=y))+
  geom_point()+
  geom_smooth(method='lm', aes(color="S1", lty="S1"), se=F)+
  geom_abline(aes(color="S2", lty="S2", slope=1, intercept=0.1))+
  theme_bw(base_size=14)+
  scale_color_manual(values=leg_col, name="Regressions", labels=leg_lab)+
  scale_linetype_manual(values=leg_lty, name="Regressions", labels=leg_lab)+
  theme(legend.text.align = 0)

What I end up with is the third line being off-set from the rest of the alignment, and the legend not being properly spaced.

Thank you for your help!

Answer 1

You can use ggtext and use element_markdown() in your theme which gives you a lot of flexibility:

library(ggplot2)
library(dplyr)
set.seed(10)
dat_sof<-tibble(x=seq(1:10))%>%
  mutate(y=x+rnorm(10))

leg_col<-c("S1"="blue", "S2"='black')
leg_lty<-c("S1"=1, "S2"=2)
leg_lab <- c("S1:<br>y = m1x + b1<br>R<sup>2</sup> = r1, n = n1",
             "S1:<br>y = m2x + b2<br>R<sup>2</sup> = r2, n = n2")
ggplot(data=dat_sof, aes(x=x, y=y))+
  geom_point()+
  geom_smooth(method='lm', aes(color="S1", lty="S1"), se=F)+
  geom_abline(aes(color="S2", lty="S2", slope=1, intercept=0.1))+
  theme_bw(base_size=14)+
  scale_color_manual(values=leg_col, name="Regressions", labels=leg_lab)+
  scale_linetype_manual(values=leg_lty, name="Regressions", labels=leg_lab)+
  theme(legend.text.align = 0,
        legend.text = ggtext::element_markdown(),
        legend.key.height=unit(2, "cm"))