geom and stat boxplot : change lower and upper whisker (ymin and ymax)

[David Hajage]

Hello,

I would like to change the default value of the lower and upper whiskers in a boxplot (from lower/upper hinge -/+ 1.5 * IQR to quantile 0.1 and 0.9).

Is there an easy way ? Or must I write my own stat_boxplot ?

Thank you very much.

[hadley wickham]

There is no easy way, basically because I'm of the strong believe that
that is not a boxplot. I agree it's a useful plot in some
circumstances, but I think it's misleading to display it in the same
way as a boxplot.

An alternative would be this:

d1 <- function(x) unname(quantile(x, 0.1))
d9 <- function(x) unname(quantile(x, 0.9))

ggplot(mpg, aes(model, cty)) +
geom_crossbar(stat = "summary", fun.y = median, fun.ymin = d1,
fun.ymax = d9) +
geom_point() +
coord_flip()

Hadley

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