Hi!
As Ben Bolker told you already, the levels are alphabetically ordered by
default.
When you print rfactor, the last line shows you the different levels, in
the saved order.
rfactor
[1] c c c d b a b d d a a e e b b e c e e a a b b b a b a e a a b d b b
c a b b
[39] d c a e c d e d a a a a
Levels: a b c d e ## here
If you want to change the order manually, do this:
rfactor=as.factor(sample(letters[1:5], 50, replace=T))
rfactor
[1] e e a a e a a a b a a d a b a b b c d c b e b e d d c a a e a b c
e b c b e
[39] a e e d b e c b e d a e ## different values because of sample()
Levels: a b c d e
rfactor2 <- factor(rfactor, levels=c("e","d","c","b","a"))
rfactor2
[1] e e a a e a a a b a a d a b a b b c d c b e b e d d c a a e a b c
e b c b e
[39] a e e d b e c b e d a e ## but the values here are the same as for
my rfactor
Levels: e d c b a ## note that the order here is the
one you typed in your call to factor(, levels=)
HTH,
Ivan
Le 12/4/2010 02:04, Rainer Schuermann a écrit :
It seems to be dependent upon the the character ("assigned alphabetically") which I found
out by manually changing the order of appearance of the characters in rfactor; the colour would
stick to the character "a", whether this appears first in rfactor or not.
I as able to control the colours being used by
boxplot(x~rfactor, col=c("2", "6", "3","5","4"))
Rgds,
Rainer
Disclaimer:
I'm new to R and very early on the learning curve - just trying my best...
On Saturday 04 December 2010 01:22:56 Eduardo Klein wrote:
Hi,
I would like to know how R assigns the numeric code to a set of factors
in a vector. For example, I have a vector of 5 different factors in a
random order, and I want a color-coded plot by factors:
rfactor=as.factor(sample(letters[1:5], 50, replace=T))
rfactor
[1] c c c d b a b d d a a e e b b e c e e a a b b b a b a e a a b d b
b c a b b
[39] d c a e c d e d a a a a
Levels: a b c d e
x=rnorm(50)
boxplot(x~rfactor, col=1:5)
So, colors 1 to 5 are assigned to factors alphabetically (a-1, b-2, ...,
e-5), or by order of appearance (c-1, d-2, b-3, a-4, e-5)? It is
possible to control that?
Saludos, EKS
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Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
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