parse two signs (==4==2*2) in ggplot2's annotate

问题

Is there a simply way to parse two equal signs in the same text in ggplot2's annotate or do I have to annotate twice? (i.e. replace : by = in the plot below?)

I can plot with annotate like this

require(ggplot2)
f <- data.frame(x = c(0, 1/1.1), y = c(1/.9, 0))
c <- ggplot(f, aes(x, y))
c + stat_smooth(method = "lm", se=F)  
+ annotate("text", x=.6,y=.75, label=(paste0("slope:","frac(1, f[1])==", 
coef(lm(f$y ~ f$x))[2])), parse=TRUE)

Which gives me this,

but I cannot have two equal signs like this,

f <- data.frame(x = c(0, 1/1.1), y = c(1/.9, 0))
c <- ggplot(f, aes(x, y))
c + stat_smooth(method = "lm", se=F)  + annotate("text", x=.6,y=.75,
label=(paste0("slope==","frac(1, f[1])==", coef(lm(f$y ~ f$x))[2])), parse=TRUE)

I get this error.

Error in parse(text = lab) : <text>:1:23: unexpected '=='
1: slope==frac(1, f[1])==
                          ^

In my real case I have several fractions, I realize that my working example is very simply and one might ask why replace : by =, but it's a working example.

回答1:

f <- data.frame(x = c(0, 1/1.1), y = c(1/.9, 0))
c <- ggplot(f, aes(x, y))
c <- c + stat_smooth(method = "lm", se=F) + annotate("text", x=.6,y=.75, label=(paste0("slope==~frac(1,f[1])==", coef(lm(f$y ~ f$x))[2])), parse=TRUE)

plot(c)

Edited. Plot is:

来源：https://stackoverflow.com/questions/33132881/parse-two-signs-4-22-in-ggplot2s-annotate