Hi.
I have a factor and I want to extract just those elements that appear
exactly once.
How to do this?
Toy example follows.
> a <- as.factor(c(rep("oak",5) ,rep("ash",1),rep("elm",1),rep
("beech",4)))
> a
[1] oak oak oak oak oak ash elm beech beech beech beech
Levels: ash beech elm oak
> table(a)
a
ash beech elm oak
1 4 1 5
>
So I would want "ash" and "elm", because there is only one ash and
only one elm in my wood.
My Best Effort:
> names(table(a)[table(a)==1])
[1] "ash" "elm"
>
This doesn't seem particularly elegant to me; there must be a better
way!
anyone?
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
tel 023-8059-7743
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