Not the prettiest code but it returns what you want. Might be slow for large dataframes.

df <- data.frame( ID=c(1,1,1,1,2,2),
                  TEST=c("A","A","B","C","B","B"),
                  RESULT=c(17,12,15,12,8,9) )


big.out <- list(NULL)

for( uID in unique(df$ID) ){
 m <- df[ df$ID == uID, , drop=FALSE ]
 run.order <- unlist(sapply( table(m$TEST), function(x) if(x > 0) 1:x) )
 m <- cbind( m, run.order=run.order )

 nr <- max(run.order)
 out <- matrix( nr=nr, nc=nlevels(m$TEST),
                dimnames=list( rep(uID, nr), levels(m$TEST) ))

 for(i in 1:nrow(m)) out[ m$run.order[i], m$TEST[i] ] <- m$RESULT[i]
 big.out[[uID]] <- out
}

do.call( "rbind", big.out )

   A  B  C
1 17 15 12
1 12 NA NA
2 NA  8 NA
2 NA  9 NA


Regards, Adai


jcarmichael wrote:
Thank you for your suggestion, I will play around with it. I guess my concern
is that I need each test result to occupy its own "cell" rather than have
one or more in the same row.


Adaikalavan Ramasamy-2 wrote:
There might be a more elegant way of doing this but here is a way of doing it without reshape().

    df <- data.frame( ID=c(1,1,1,1,2,2),
                      TEST=c("A","A","B","C","B","B"),
                      RESULT=c(17,12,15,12,8,9) )

    df.s <- split( df, df$ID )

    out  <- sapply( df.s, function(m)
                    tapply( m$RESULT, m$TEST, paste, collapse="," ) )

    t(out)

      A       B     C
    1 "17,12" "15"  "12"
    2 NA      "8,9" NA

Not the same output as you wanted. This makes more sense unless you have a reason to priotize 17 instead of 12 in the first row.

Regards, Adai


jcarmichael wrote:
I have a dataset in "long" format that looks something like this:

ID   TEST    RESULT
1       A          17
1       A          12
1       B          15
1       C          12
2       B           8
2       B           9

Now what I would like to do is transpose it like so:

ID    TEST A    TEST B    TEST C
1         17           15          12
1         12            .            .
2          .             8            .
2          .             9            .

When I try:

reshape(mydata, v.names="result", idvar="id",timevar="test",
direction="wide")

It gives me only the first occurrence of each test for each subject.  How
can I transpose my dataset in this way without losing information about
repeated tests?

Any help or guidance would be appreciated!  Thanks!
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