On Tue, Sep 29, 2009 at 6:47 PM, chipmaney chipma...@hotmail.com wrote:
I have a dataset. Initially, it has 25 levels for a certain factor,
Description.
However, I then subset it, because I am only interested in 2 of the 25
factors. When I subset it, I get the following. The vector lists only the
two factors, yet there remain 25 levels:
Quadrats.df$Description
[1] Emergent 25x75 Emergent 25x75 Emergent 25x75 Emergent 25x75
Emergent 25x75 Emergent 25x75 Emergent 25x75 Emergent 25x75 Emergent
25x75
[10] Emergent 25x75 Emergent 25x75 Emergent 25x75 Emergent 25x75
Emergent 25x75 Emergent 25x75 Hydroseed 25x75 Hydroseed 25x75 Hydroseed
25x75
[19] Hydroseed 25x75 Hydroseed 25x75 Hydroseed 25x75 Hydroseed 25x75
Hydroseed 25x75 Hydroseed 25x75 Hydroseed 25x75 Hydroseed 25x75 Hydroseed
25x75
[28] Hydroseed 25x75 Hydroseed 25x75 Hydroseed 25x75 Hydroseed 25x75
25 Levels: Black Cottonwood Black Cottonwood Enhanced Emergent Emergent
25x75 Floodplain 1 Floodplain 2 Floodplain 3 Hydroseed 25x75 ... Western Red
Cedar Enhanced
This seems rather innocuous; however, when I run a by statement, it returns
a list with 25 entries, 23 of which are of course NAis there a way to
avoid this?
Just re-factor() it when you select a subset - and also it's nice if
you give us a simple example - all your Emergent this and Hydroseed
doesn't look very clear!
Like this:
# make a factor:
x=factor(sample(letters,10))
x
[1] z x f i n b y e p c
Levels: b c e f i n p x y z
# a subset:
x[1:3]
[1] z x f
Levels: b c e f i n p x y z
# - still has all the levels. So re-factor():
factor(x[1:3])
[1] z x f
Levels: f x z
et voila?
Barry
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
