Insertion of leq symbol in substitute, Mathematical Annotation in R

Question

I have the following graph:

library(tidyverse)

mm<-70
sdm<-12
weight_lim<-c(30, 110)
xrange<-55
ggplot(data = data.frame(weight = weight_lim), aes(weight)) +
  stat_function(fun = dnorm, n = 101, args = list(mean = mm, sd = sdm),color=1) +
  ylab("f(weight)") + scale_x_continuous(breaks=seq(weight_lim[1],weight_lim[2], by=5)) + 
  stat_function(fun = dnorm, args = list(mean = mm,sd=sdm),
                xlim = c(weight_lim[1],xrange[1]),
                geom = "area",fill="red",alpha=0.5)+
  annotate("text", x = 40, y = .02, 
           label = substitute(paste("P(X < ",v," ) = ",s),list(v=format(xrange, nsmall = 1),s=round(pnorm(xrange,mm,sdm),4))),
           size=3 , fontface="bold")+
  theme_bw()
#> Warning in is.na(x): is.na() applied to non-(list or vector) of type 'language'

^{Created on 2020-08-22 by the reprex package (v0.3.0)}

I would like to replace “<” by "less than or equal to" sign in

substitute(paste("P(X < ",v," ) = ",s),list(v=format(xrange, nsmall = 1),s=round(dnorm(xrange,mm,sdm),4)))

Answer 1

One of the easiest ways to insert a character is to use the \u escape sequence. It's used just like any of the other escape sequences, where the Unicode character code follows \u. You can see the example here:

library(ggplot2)

ggplot(mtcars, aes(disp, mpg)) + geom_point() + theme_classic() +
  annotate('text', x=300, y=29, label='Unicode 2264: \u2264') +
  annotate('text', x=300, y=26, label='Unicode 2265: \u2265')

As you can see, less than or equal to is Unicode 2264, so just use \u2264 directly in your label.

Answer 2

If you have

vv = format(xrange, nsmall = 1)
ss = round(dnorm(xrange,mm,sdm),4)

Then either of these will work.

lab = bquote(P(X <= .(vv)) == .(ss)) 
# or
lab = substitute(P(X <= v) == s, list(v=vv, s=ss))

p + annotate("text", x = 40, y = .02, label = deparse(lab), parse=TRUE)

Noting from annotate a formula (with bqoute or substitute) in R (ggplot) gives Error that annotate doesn't take expressions., hence the deparse/parse stuff to get rid of the warnings.