Ordering the levels of a vector
On 12/3/07, Judith Flores <juryef at yahoo.com> wrote:
Hi,
I have a vector in a data frame that looks
something like this:
day<-c('Day -1','Day 6','Day 10')
This vector specifies the order in which several
panel will appear in a lattice plots. But the order in
which such plots will appear will be the following:
Day -1, Day 10, Day 6. Which makes sense, but I cannot
name the Days like this: Day -01,Day 10, Day 06, which
would put the levels in the order I want them to be.
Now, this vector won't always have the same values,
it could be:
day<-c('Day -1, 'Day 2','Day 14')
So I cannot set the levels manually:
levels(day)<-c('Day -1', 'Day something','Day
something else')
Well, you need some sort of rule that can be used to determine the
order of the levels. The default (see ?factor) is 'levels =
sort(unique(x))'. If you instead want, say, levels in the order of
first appearance (assuming that's what you mean by "original order"),
you could define
my.factor = function(x) { factor(x, levels = unique(x)) }
and then use
day<- my.factor(c('Day -1','Day 6','Day 10'))
day
[1] Day -1 Day 6 Day 10 Levels: Day -1 Day 6 Day 10
I tried as.ordered, but I guess I am not using the right function. How can I command the script to put the panels in the original order given of the vector in a data frame?
-Deepayan