Align legend text in ggplot

Question

I have difficulty in aligning the legend text to the left.

library(ggplot2)
library(reshape2)
o3<- rnorm(1827, 50, 10)
NO2<- rnorm(1827, 35, 7)
NOx<         


        

Answer 1

You need to specify legend.text.align in theme():

ggplot(meltdf, aes(x = date, y = value, colour =variable)) + 
geom_smooth() + 
stat_smooth(method = "gam") +
scale_color_discrete(name="Pollutant", 
    labels = c(expression(O[3]),
               expression(NO[2]),
               expression(NO[x]),
               expression(PM[2.5]))) +
theme(legend.text.align = 0)

Alternatively, try using bquote instead of expression, and default left alignment takes place. I don't know why just using expression changes the alignment to the right...

ggplot(meltdf, aes(x = date, y = value, colour =variable)) + 
geom_smooth() + 
stat_smooth(method = "gam") +
scale_color_discrete(name="Pollutant", 
    labels = c(bquote(O[3]),
               bquote(NO[2]),
               bquote(NO[x]),
               bquote(PM[2.5])))