r - How does plot.cld in multcomp package calculate boxes? -

to visualise significant differences letters there plotting function in multcomp package:

library(multcomp) tuk <- glht(model, linfct = mcp(effect = "tukey")) plot(cld(tuk)) 

how boxes calculated (i.e. upper , lower quartiles , whiskers)? not find information in documentation.

this regular boxplot. instance warpbreaks data:

# load data data(warpbreaks) # model  amod <- aov(breaks ~ tension, data = warpbreaks) tuk <- glht(amod, linfct = mcp(tension = "tukey")) # plot plot(cld(tuk)) 

this pretty same

boxplot(breaks ~ tension, data = warpbreaks) # or boxplot(split(warpbreaks$breaks, warpbreaks$tension)) 

boxplot uses boxplot.stats, uses stats.fivenum calculate necessary statistics. notice differs quantile function probs=c(0,.25, .5, .75, 1) , na.rm=true. in simplest form (no na's, length>0), fivenum looks this:

fivenum <- function (x)  {   x <- sort(x)   n <- length(x)   n4 <- floor((n + 3)/2)/2   d <- c(1, n4, (n + 1)/2, n + 1 - n4, n)   0.5 * (x[floor(d)] + x[ceiling(d)]) }