[R] Data frame referencing?
Sander Oom
slist at oomvanlieshout.net
Fri Aug 4 14:26:48 CEST 2006
Dear Gabor and Dimitris,
Simple, once you know! It is these little exceptions on the R notation
that get me stuck. Now I am on the loose again!
Thanks,
Sander.
Dimitris Rizopoulos wrote:
> you need to use quotes, i.e.,
>
> a[a$y > 0.5, "y"] <- 1
>
> you can also use
>
> a$y[a$y > 0.5] <- 1
>
>
> I hope it helps.
>
> Best,
> Dimitris
>
> ----
> Dimitris Rizopoulos
> Ph.D. Student
> Biostatistical Centre
> School of Public Health
> Catholic University of Leuven
>
> Address: Kapucijnenvoer 35, Leuven, Belgium
> Tel: +32/(0)16/336899
> Fax: +32/(0)16/337015
> Web: http://med.kuleuven.be/biostat/
> http://www.student.kuleuven.be/~m0390867/dimitris.htm
>
>
> ----- Original Message -----
> From: "Sander Oom" <slist at oomvanlieshout.net>
> To: <r-help at stat.math.ethz.ch>
> Sent: Friday, August 04, 2006 1:48 PM
> Subject: [R] Data frame referencing?
>
>
>> Dear R users,
>>
>> When you do:
>>> x <- rnorm(10)
>>> y <- rnorm(10)
>>> z <- rnorm(10)
>>> a <- data.frame(x,y,z)
>>> a$x
>> [1] 1.37821893 0.21152756 -0.55453182 -2.10426048 -0.08967880
>> 0.03712110
>> [7] -0.80592149 0.07413450 0.15557671 1.22165341
>>
>> Why does this not work:
>>> a[a$y>0.5,y] <-1
>> Error in "[<-.data.frame"(`*tmp*`, a$y > 0.5, y, value = 1) :
>> only 0's may be mixed with negative subscripts
>>
>> While this works:
>>> a[a$y>0.5,2] <-1
>>> a
>> x y z
>> 1 1.37821893 -1.0887363 1.7340522
>> 2 0.21152756 -0.7256467 -1.3165373
>> 3 -0.55453182 1.0000000 -2.1116072
>> 4 -2.10426048 -0.4898596 -1.5863823
>> 5 -0.08967880 1.0000000 -0.9139706
>> 6 0.03712110 1.0000000 -1.3004970
>> 7 -0.80592149 -0.7004193 -0.1958059
>> 8 0.07413450 1.0000000 -1.3574303
>> 9 0.15557671 -0.3335407 -2.1991236
>> 10 1.22165341 1.0000000 -0.7576708
>>
>> For a complex loop I would prefer to reference the right colomn by
>> name,
>> not by number! Now, when the colomns change, I need to check my code
>> to
>> make sure that the right colomns are referenced.
>>
>> Suggestions much appreciated!
>>
>> Thanks in advance,
>>
>> Sander.
>>
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>> PLEASE do read the posting guide
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>>
>
>
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