[R] Selecting Variables
jim holtman
jholtman at gmail.com
Tue Aug 5 16:09:59 CEST 2008
I am not sure where the "Max" comes from, but this might be a start for you:
> x <- read.table(textConnection("ID Exposure_1 Exposure_2 Exposure_3
+ 1 y y y
+ 2 y y -
+ 3 y - -"), header=TRUE, na.strings='-')
> closeAllConnections()
> require(reshape)
> y <- melt(x, id.var='ID')
> # get rid of NAs
> y <- y[complete.cases(y),]
> y
ID variable value
1 1 Exposure_1 y
2 2 Exposure_1 y
3 3 Exposure_1 y
4 1 Exposure_2 y
5 2 Exposure_2 y
7 1 Exposure_3 y
> cbind(Unique=tapply(y$ID, y$ID, length))
Unique
1 3
2 2
3 1
>
On Tue, Aug 5, 2008 at 9:21 AM, Michael Pearmain <mpearmain at google.com> wrote:
> Hi All,
>
> i have a dataset that i want to dynamically inspect for the number of
> variables that start with "Exposure_" and then for these count the entries
> across each case i.e
>
> ID Exposure_1 Exposure_2 Exposure_3
> 1 y y y
> 2 y y -
> 3 y - -
>
> So the corresponding new variables that would be created are
>
> ID Max_Exposure Unique_Exposure
> 1 3 3
> 2 3 2
> 3 3 1
>
> I know this may seem fairly basic but it will give me the starting point to
> develop more advanced things with loop and nat lang
>
> Thanks in advance
>
> Mike
>
> [[alternative HTML version deleted]]
>
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--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
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