[R] what does boxplot draw?
Wladimir Eremeev
wl at eimb.ru
Sun May 11 15:03:06 CEST 2003
Dear r-help,
Unfortunately I cannot find in the documentation what determines
ranges of a 'box' in the box-and-whisker plot.
It is said in "Simple R" (http://www.math.csi.cuny.edu/Statistics/R/simpleR)
that they are 1st and 3rd Qus usually.
I tried to add to boxplot lines with (quantile(x,probs=0.25)), but
lines do not coincide with edges of boxes.
Here's the example. I've got 3 vectors of values, x1,x2,x3
The command
boxplot(list(x1,x2,x3))
draws 3 box-and-whisker diagrams.
Commands
lines(c(quantile(x1,probs=c(0.25)),quantile(x2,probs=c(0.25)),quantile(x3,probs=c(0.25))))
lines(c(quantile(x1,probs=c(0.75)),quantile(x2,probs=c(0.75)),quantile(x3,probs=c(0.75))))
draw lines with y values of quantiles.
Lines ends are close to the box edges but not exactly on them.
While command
lines(c(median(x1),median(x2),median(x3)))
puts lines with ends exactly on the middle line of the box-and-whisker
plots.
--
Best regards
Wladimir Eremeev mailto:wl at eimb.ru
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