[R] Ordering boxplot factors
MSchwartz at mn.rr.com
Fri Jan 6 03:48:01 CET 2006
On Thu, 2006-01-05 at 20:27 -0600, Joseph LeBouton wrote:
> Hi all,
> what a great help list! I hope someone can help me with this puzzle...
> I'm trying to find a simple way to do:
> so that the factors are ordered left-to-right along the x-axis by
> median, not alphabetically by factor name.
> Complicated ways abound, but I'm hoping for a magical one-liner that'll
> do the trick.
> Any suggestions would be treasured.
Using the first example in ?boxplot, which is:
boxplot(count ~ spray, data = InsectSprays, col = "lightgray")
Get the medians for 'count by spray' using tapply() and then sort the
results in increasing order, by median:
med <- sort(with(InsectSprays, tapply(count, spray, median)))
C E D A F B
1.5 3.0 5.0 14.0 15.0 16.5
Now do the boxplot, setting the factor levels in order by median:
boxplot(count ~ factor(spray, levels = names(med)),
data = InsectSprays, col = "lightgray")
So...technically two lines of code.
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