[R] reshaping data

[Peter Ehlers]

On 2012-07-24 22:01, Rui Barradas wrote:
> Hello,
>
> Try the following.
>
>
> # We are going to use this twice
> sl <- split(long, long$id)
>
> # Remove groups with only one row
> l2 <- lapply(sl, function(x) if(nrow(x) > 1) x)
> l2 <- do.call(rbind, l2)
> l2
>
> # Create a new variable
> l3 <- lapply(sl, function(x) cbind(x, NEW_VARIABLE=seq_len(nrow(x))))
> l3 <- do.call(rbind, l3)
> l3
>
>
> Hope this helps,
>
> Rui Barradas

Another way is to use ave() to construct a
variable (I call it z below) to indicate
which rows to keep. We'll also construct
a variable 'count' to satisfy the additional
request.

   long1 <- transform(long,
              count= ave(id, id,
                       FUN = function(x) seq_len(length(x))),
              z = ave(id, id, FUN = length))

   long2 <- subset(long1, z > 1, -z)

Peter Ehlers

>
> Em 25-07-2012 01:59, AC Del Re escreveu:
>> Hi,
>>
>> I am trying to reshape data from a long to wide format but have a specific
>> task that I cannot get to output properly.
>>
>> # SAMPLE DATA;
>> id <- c(1,2,2,3,3,3)
>> time <-c(0,0,5, 0, 2, 10)
>> x <- rnorm(length(id))
>> long <- data.frame(id,time,x)
>>
>> # To reshape, I would like to exclude 'id' values that have NO duplicate
>> (i.e., remove
>> #  id=1 in this case). My attempts failed because the functions removes the
>> first value of each id (and I would like to preserve them if length of each
>> unique id >1), e.g.:
>>
>> junk <- long[duplicated(long$id),]  # REMOVES TOO MANY ROWS!
>> junk <-subset(long, seq(id) - match(id,id) >0) # SAME
>>
>> Essentially, I  would like to preserve all values of an id with more than
>> one row. Any ideas are much appreciated.
>>
>> In addition, is there an easy way to create a new variable based on the
>> number of instances of each id (in the long dataset)? e.g.
>>
>> id time           x                NEW_VARIABLE
>> 1  1    0 -0.03921791     1
>> 2  2    0 -1.07869262     1
>> 3  2    5  1.73442621     2
>> 4  3    0 -0.64356207     1
>> 5  3    2  1.19691074     2
>> 6  3   10  0.62035225    3
>>
>> Thank you,
>>
>> AC
>>
>> 	[[alternative HTML version deleted]]
>>
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>
> ______________________________________________
> R-help at r-project.org 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.
>