ggplot x-axis ticks for pcc outcome - need symbols and scale_x_discrete not working

I've run a sensitivity analysis using the LHS-PRCC technique for 16 parameters and 10,000 different parameter sets. The outcome is a large pcc. (I'll give a generic example using 100)

df <- cbind(
    pcb = runif(100,0,1),
    pbc = runif(100,0,1),
    psb = runif(100,0,1),
    pbs = runif(100,0,1),
    pci = runif(100,0,1),
    pic = runif(100,0,1),
    psi = runif(100,0,1),
    pis = runif(100,0,1),
    epsilonc = runif(100,0,1),
    epsilons = runif(100,0,1),
    gammac = runif(100,0,1),
    gammas = runif(100,0,1),
    tauc = runif(100,0,1),
    taus = runif(100,0,1),
    sigmab = runif(100,0,1),
    sigmai = runif(100,0,1),
summary.statistic = runif(100,0,1))

bonferroni.alpha <- 0.05/16
PRCC <- pcc(df[ , 1:16], df[ ,17], nboot = 10000, rank = TRUE, conf = 1- bonferroni.alpha)

I'm really struggling with the formatting of the ggplot

plot <- ggplot(PRCC, mapping = aes(), environment = parent.frame(), ylim = c(-1,1)) + ggtitle("PRCC")

This works fine but I want to use symbols and subscript for the x-axis ticks.

I've tried this, but the x-axis ticks just disappear.

plot <- ggplot(PRCC, mapping = aes(), environment = parent.frame(), ylim = c(-1,1)) + ggtitle("PRCC") + 
scale_x_discrete(breaks=c("pcb","pbc","psb","pbs", "pci","pic", "epsilonc","epsilons","gammac","gammas", "tauc","taus", "sigmab", "sigmai"),labels=c((expression(p[cb])), (expression(p[bc])), (expression(p[sb])), (expression(p[bs])), (expression(p[ci])), (expression(p[ic])), (expression(Epsilon[c])),(expression(Epsilon[s])),(expression(Gamma[c])),(expression(Gamma[s])),(expression(Tau[c])),(expression(Tau[s])),(expression(Sigma[b])),(expression(Sigma[i]))))

Solution

The issue is that you have a continuous x scale, i.e. you have to use scale_x_continuous to set the labels. For this reason you also have to use numbers for the breaks=. Finally note that you missed two labels.

library(sensitivity)
library(ggplot2)

set.seed(123)

bonferroni.alpha <- 0.05 / 16

PRCC <- pcc(
  df[, 1:16], df[, 17],
  nboot = 10, rank = TRUE, conf = 1 - bonferroni.alpha
)

p <- ggplot(PRCC) +
  ggtitle("PRCC")

p +
  scale_x_continuous(
    breaks = 1:16,
    labels = c(
      expression(p[cb]),
      expression(p[bc]),
      expression(p[sb]),
      expression(p[bs]),
      expression(p[ci]),
      expression(p[ic]),
      expression(p[si]),# Missing = psi
      expression(p[is]),# Missing = pis
      expression(Epsilon[c]),
      expression(Epsilon[s]),
      expression(Gamma[c]),
      expression(Gamma[s]), 
      expression(Tau[c]), 
      expression(Tau[s]), 
      expression(Sigma[b]), 
      expression(Sigma[i])
    )
  )