Re: [R] unequal number of observations for longitudinal data

From: gallon li <gallon.li_at_gmail.com>
Date: Sat 27 Jan 2007 - 11:22:04 GMT

Two questions:

  1. How do I replace "NA" with 0?
  2. How can I sort the observations by their id instead of by time? (actually i can see what you produced is automatically sorted by id; but in my case, the output data is sorted by time)

On 1/27/07, Chuck Cleland <ccleland@optonline.net> wrote:
>
> gallon li wrote:
> > i have a large longitudinal data set. The number of observations for
> each
> > subject is not the same across the sample. The largest number of a
> subject
> > is 5 and the smallest number is 1.
> >
> > now i want to make each subject to have the same number of observations
> by
> > filling zero, e.g., my original sample is
> >
> > id x
> > 001 10
> > 001 30
> > 001 20
> > 002 10
> > 002 20
> > 002 40
> > 002 80
> > 002 70
> > 003 20
> > 003 40
> > 004 ......
> >
> > now i wish to make the data like
> >
> > id x
> > 001 10
> > 001 30
> > 001 20
> > 001 0
> > 001 0
> > 002 10
> > 002 20
> > 002 40
> > 002 80
> > 002 70
> > 003 20
> > 003 40
> > 003 0
> > 003 0
> > 003 0
> > 004 ......
> >
> > so that each id has exactly 5 observations. is there a function which
> can
> > allow me do this quickly?
>
> Filling in with zeros seems like a bad idea, but here is an approach
> to filling in with NAs. I will leave replacing the NAs with zeros to you.
>
> df.long <- data.frame(id = c(1,1,1,2,2,2,2,2,3,3), x = runif(10),
> time = c(1,2,5,1,2,3,4,5,2,4))
>
> df.long
> id x time
> 1 1 0.72888215 1
> 2 1 0.60893548 2
> 3 1 0.41347690 5
> 4 2 0.79388248 1
> 5 2 0.05810054 2
> 6 2 0.02451654 3
> 7 2 0.85464775 4
> 8 2 0.15970365 5
> 9 3 0.22856183 2
> 10 3 0.38291471 4
>
> df.wide <- reshape(df, idvar = "id", v.names = "x", direction="wide")
>
> df.wide
> id x.1 x.2 x.5 x.3 x.4
> 1 1 0.6375135 0.1651258 0.3210223 NA NA
> 4 2 0.9878134 0.8909020 0.9853269 0.7747615 0.3834130
> 9 3 NA 0.3586109 NA NA 0.8310539
>
> df.long2 <- reshape(df.wide, direction="long")
>
> df.long2
> id time x
> 1.1 1 1 0.6375135
> 2.1 2 1 0.9878134
> 3.1 3 1 NA
> 1.2 1 2 0.1651258
> 2.2 2 2 0.8909020
> 3.2 3 2 0.3586109
> 1.5 1 5 0.3210223
> 2.5 2 5 0.9853269
> 3.5 3 5 NA
> 1.3 1 3 NA
> 2.3 2 3 0.7747615
> 3.3 3 3 NA
> 1.4 1 4 NA
> 2.4 2 4 0.3834130
> 3.4 3 4 0.8310539
>
> This assumes that your data in the "long" format has a time variable.
> See the help page for reshape() for more details.
>
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> --
> Chuck Cleland, Ph.D.
> NDRI, Inc.
> 71 West 23rd Street, 8th floor
> New York, NY 10010
> tel: (212) 845-4495 (Tu, Th)
> tel: (732) 512-0171 (M, W, F)
> fax: (917) 438-0894
>

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sat Jan 27 22:29:53 2007

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