Demonstration of integration of plotting individuals chart using qcc and ggplot2, with annotation outside of the plot.

annotate_outside_plot.R

library(qcc)
library(ggplot2)
library(grid)

#' The data, from sample data provided by Donald Wheeler
my.xmr.raw <- c(5045,4350,4350,3975,4290,4430,4485,4285,3980,3925,3645,3760,3300,3685,3463,5200)

#' Create the individuals qcc object
my.xmr.x <- qcc(my.xmr.raw, type = "xbar.one", plot = FALSE)

#' create a data frame from the individuals qcc object
my.xmr.df <- data.frame(index = 1:length(my.xmr.raw), x = my.xmr.raw)

#' Make pretty axis limits so we can use them later for positioning text
my.ylim <- range(c(my.xmr.x$statistics, my.xmr.x$limits[2], my.xmr.x$limits[1]))
my.xlim <- range(1:length(my.xmr.x$statistics))

#' Create the basic graph
#' Set font sizes to be consistent between ggplot elements and grid elements
my.p <- ggplot(data = my.xmr.df) +
  theme(text = element_text(size = 24),
        plot.margin = unit(c(2,4,1,1), "char")) +
  scale_x_continuous(expand = c(0, 0.5), limits = my.xlim) +
  geom_point(aes(x = index,y = x),shape = 20) +
  geom_line(aes(x = index,y = x)) +
  geom_point(aes(x = index[x > 5100],y = x[x > 5100]),shape = 19,colour = '#ff0033')

#' 
my.p <- my.p +
  ylim(my.ylim)

# draw the UCL and LCL lines
my.p <- my.p +
  stat_hline(yintercept = my.xmr.x$limits[2],linetype = 2) +
  stat_hline(yintercept = my.xmr.x$limits[1],linetype = 2)

#' Label the limits
my.p <- my.p +
  annotation_custom(grob = textGrob("LCL", hjust = 0, gp = gpar(fontsize = 24)), 
                    xmin = length(my.xmr.x$statistics) + 0.6,
                    xmax = length(my.xmr.x$statistics) + 0.6, 
                    ymin = my.xmr.x$limits[1], 
                    ymax = my.xmr.x$limits[1])
my.p <- my.p +
  annotation_custom(grob = textGrob("UCL", hjust = 0, vjust = 0.5, gp = gpar(fontsize = 24)), 
                    xmin = length(my.xmr.x$statistics) + 0.6,
                    xmax = length(my.xmr.x$statistics) + 0.6, 
                    ymin = my.xmr.x$limits[2], 
                    ymax = my.xmr.x$limits[2])

#' Draw the center line
my.p <- my.p +
  stat_hline(yintercept = my.xmr.x$center, linetype = 1)
#' and label it
my.p <- my.p +
  annotation_custom(grob = textGrob("CL", hjust = 0, vjust = 0.5, gp = gpar(fontsize = 24)), 
                    xmin = length(my.xmr.x$statistics) + 0.6,
                    xmax = length(my.xmr.x$statistics) + 0.6, 
                    ymin = my.xmr.x$center, 
                    ymax = my.xmr.x$center)

#' And now the magic: disable clipping so the labels can be plotted outside the plot region
my.gt <- ggplot_gtable(ggplot_build(my.p))
my.gt$layout$clip[my.gt$layout$name == "panel"] <- "off"

#' Finally, draw the graph
grid.draw(my.gt)

love the idea of using the qcc module stats this way. Nicely done.