Use ampersand in ggplot facet strip label

Question

How can I use an ampersand in a facet strip label? I have tried as is, and using unicode with the same result.

MWE

library(ggplot2)

mtcars$am2 <- factor(mtcars$am, labels=c("N[one]==1 \U0026 N[one]==1", 
                                         "N[two]==2 & N[two]==2"))

ggplot(mtcars, aes(mpg, wt)) + 
    facet_grid(. ~ am2, labeller = label_parsed)

I am using Windows 7 , R3.4.4. Thanks

I'm guessing here ... is `&` being interpreted as the vector "and" operator, and therefore turned from a special function to a proper prefix notation? That is, in R `a & b` is equivalent to `\`&\`(a, b)`, I wonder if that's what's happening under the hood. (I can't find mention of `&` in `plotmath` or related.) — r2evans, Oct 22 '18 at 14:44

score 2 · Accepted Answer · answered Oct 22 '18 at 16:41

The solution is to quote the & and use ~ instead of white spaces as is usual in expressions.

"N[two]==2~'&'~N[two]==2"

I'm not entirely sure what is going on here, except, as r2evans suggests in the comments, that the unquoted & is being interpreted as an infix operator.

Use ampersand in ggplot facet strip label

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