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 NA....is 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.
