Only display every n data point in ggplot2

everyn.R

# Function to set all vector items to blank except for every nth item

everyn <- function(myvec, n){
  myvec <- sort(unique(myvec))
  for(i in 1:length(myvec)) {
    if( i %% n != 1) {
      myvec[i] <- ""
    }
  }
  return(myvec)
}

# Then add this line to your ggplot graph, where mydf is the data frame with data being graphed, xcol is the unquoted name of the x-axis column, and n is every nth item you want to display:

scale_x_discrete(labels = everyn(mydf$xcol, n))