Hello,

I don't see the problem.


d <- read.table(text="
ParticipID    ERP   Electrode
1         s1  0.0370       FP1
2         s2 35.0654       FP2
3         s3 -3.3852        F4
4         s4  2.6119        P3
5         s5  0.1224        P4
6         s6 -5.3153        O1
", header=TRUE)
str(d)

wanted <- c("FP1", "FP2", "F4")
subset(d, Electrode %in% wanted)
#output
#  ParticipID     ERP Electrode
#1         s1  0.0370       FP1
#2         s2 35.0654       FP2
#3         s3 -3.3852        F4

But if you can't subset because the variable Electrode is a factor, use 
as.character(Electrode).

Hope this helps,

Rui Barradas

Em 10-08-2012 10:07, simona mancini escreveu:
> Hi,
>
>
> I need to subset different levels of vector in a dataset to create a new dataframe that contains only these. These observations are not numerical, so I can't use the subset() function (at least this is the response I get from R).
> Suppose the dataframe looks like this:
>
>
>
>    ParticipID    ERP   Electrode
> 1         s1  0.0370       FP1
> 2         s2 35.0654       FP2
> 3         s3 -3.3852        F4
> 4         s4  2.6119        P3
> 5         s5  0.1224        P4
> 6         s6 -5.3153        O1
>
>
> I want to create a subset of the dataframe with only the FP1, FP2, F4 levels of Electrode, how do I do?
> (actually the levels I have to filter are much more than these three, but this is just to give an example).
>
> I know this is a trivial question, but I am still getting familiar with R...
>
> Thanks a lot,
>
> s.
>
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>
>
>
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