Reorder in decreasing order

Hi Duncan,

That was my original suggestioin.  His reply suggests that it is not that he wanted.

"

Not quite. It still orders the values in an increasing order, you've
just changed the values here. I'm using reorder() to prepare for
plotting the values, so I can't change the values."


bymean2<-with(InsectSprays,reorder(spray,count,function(x) -mean(x)))

   bymean2
   [1] A A A A A A A A A A A A B B B B B B B B B B B B C C C C C C C C C C C C D D
[39] D D D D D D D D D D E E E E E E E E E E E E F F F F F F F F F F F F
attr(,"scores")
           A          B          C          D          E          F
-14.500000 -15.333333  -2.083333  -4.916667  -3.500000 -16.666667
####################
Levels: F B A D E C
#######################

A.K.



----- Original Message -----
From: Duncan Murdoch <murdoch.duncan at gmail.com>
To: Sverre Stausland <johnsen at fas.harvard.edu>
Cc: r-help at r-project.org
Sent: Sunday, July 22, 2012 4:56 PM
Subject: Re: [R] Reorder in decreasing order

On 12-07-22 12:27 PM, Sverre Stausland wrote:

reorder() is probably the best way to order the levels in a vector
without manually specifying the order. But reorder() orders by default
in an increasing order: "The levels are ordered such that the values
returned by ?FUN? are in increasing order."

Is there a way to do what reorder() does, but order the levels
according to a _decreasing_ order of the values?

Yes, as Weidong suggested:

x <- rnorm(20)
y <- factor(sample(letters[1:3], 20, replace=TRUE))
reorder(y, x, mean)

[1] a a c c c b b a b a c c b b a a a a c a
attr(,"scores")
          a          b          c
-0.2012975  0.6117830  0.2180352
Levels: a c b

reorder(y, x, function(x) -mean(x))

[1] a a c c c b b a b a c c b b a a a a c a
attr(,"scores")
          a          b          c
0.2012975 -0.6117830 -0.2180352
Levels: b c a

Duncan Murdoch