R - parse function doesn't work as expected

Question

In the following example (please notice differences in y-axis labels) I use a variable to fill in an axis label in ggplot2. Interestingly ~ produces much larger spaces, and extra spaces show up around an enlarged -.

library(ggplot2)

#LabelY <- "Miles per Gallon-Car"
LabelY <- parse(text="Miles~per~Gallon-Car")

a <- ggplot(mtcars, aes(x=wt, y=mpg)) + geom_point() +
        ggtitle("Fuel Efficiency of 32 Cars") +
        xlab(LabelY) + ylab(LabelY) +
        theme(text=element_text(size=16))
print(a)

I am using parse because it allows me to use more complex examples including atop and greek letters.

Is there a way I can make use of parse to import complex strings while also preserving the desired "less spread out" appearance of the content?

Answer 1

It looks like enclosing the hyphenated term with backticks will allow you to keep the hyphen instead of turning it in a dash.

Here I put the new hyphenated version of the axis label on the x axis and leave the y axis as the original for comparison.

LabelY <- parse(text="Miles~per~Gallon-Car")
LabelY2 <- parse(text="Miles~per~`Gallon-Car`")

ggplot(mtcars, aes(x=wt, y=mpg)) + geom_point() +
    ggtitle("Fuel Efficiency of 32 Cars") +
    xlab(parse(text = LabelY2)) + ylab(LabelY) +
    theme(text=element_text(size=16))

As you pointed out in the comments, you can also use a curly bracket and single quote combination around the hyphenated term to get the same effect.

parse(text="Miles~per~{'Gallon-Car'}")