How Can I Make geom_label Display Slightly Complex R Regular Expressions?

[Donald Macnaughton]

Hello Group,

I would like to be able to have ggplot show parsed R regular expressions in labels on plots. In particular, I would like to display the string

Area a1

where the second "a" is in italics, and the 1 is a subscript. Here's some code to produce the problem:

# The following approaches work work properly with parse=TRUE:

# label = "italic(a[1])"

# label = "plain(Area)"

# But the following DON'T WORK:

# label = "plain(Area ) italic(a[1])"

# label = "plain(Area ), italic(a[1])"

# Note that the PDF ggplot2 manual for version 2.2.1 says on page 74 that

# "geom_text uses strings, not expressions". The geom_label function and 

# the geom_text function are variants, both described under the heading

# geom_label.

# Regular expressions in R 3.4.0 are described in the Reference Index manual

# under  plotmath  beginning on page 752.

library(ggplot2)

x <- c(1,2)

y <- c(3,4)

df <- data.frame(x,y)

ggplot(df, aes(x,y)) +  geom_path() + 

geom_label(label="plain(Area ) italic(a[1])", x=1.5,y=3.75,parse=TRUE)

Thank you for your help,

Don Macnaughton

[Olivia]

Try the following:

ggplot(df, aes(x,y)) +  geom_path() + 

geom_label(label="plain(Area )~italic(a[1])", x=1.5,y=3.75,parse=TRUE)

Replace the ~ with a * if you prefer no gap in other settings.

Cheers,

Olivia