Harold -
Here's what I came up with:
tapply(as.vector(as.matrix(dat[5:7])),
+ list(rep(dat$id,3),as.vector(as.matrix(dat[2:4]))),I)
item1 item10 item2 item3 item4 item5 item7 item9
1 NA NA 1 NA NA 1 NA 0
2 0 NA NA NA NA 1 1 NA
3 1 NA 0 1 NA NA NA NA
4 NA NA NA 1 0 NA 0 NA
5 NA 1 NA 0 1 NA NA NA
I thought there would be a way to use xtabs, but I had
trouble preserving the NAs.
The columns aren't in the right order, and the item6 column is
missing, but it's pretty close.
Thanks for the easily reproducible example, and the interesting
puzzle.
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Thu, 25 Feb 2010, Doran, Harold wrote:
Suppose I have a data frame like "dat" below. For some context, this is the
format that represents student's taking a computer adaptive test. first.item is the first
item that student was administered and then score.1 is the student's response to that
item and so forth.
item.pool <- paste("item", 1:10, sep = "")
set.seed(54321)
dat <- data.frame(id = c(1,2,3,4,5), first.item = sample(item.pool, 5,
replace=TRUE),
second.item = sample(item.pool, 5,replace=TRUE), third.item =
sample(item.pool, 5,replace=TRUE),
score1 = sample(c(0,1), 5,replace=TRUE), score2 = sample(c(0,1),
5,replace=TRUE), score3 = sample(c(0,1), 5,replace=TRUE))
I need to restructure this into a new format. The new matrix df (after the
loop) is exactly what I want in the end. But, I'm annoyed at myself for not
thinking of a more efficient way to restructure this without using a loop.
df <- matrix(NA, ncol = length(item.pool), nrow = nrow(dat))
colnames(df) <- unique(item.pool)
for(i in 1:5){
for(j in 2:4){
rr <- which(dat[i,j] == colnames(df))
df[i,rr] <- dat[i, (j+3)]
}
}
Any thoughts?
Harold
[[alternative HTML version deleted]]
______________________________________________
R-help@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.
______________________________________________
R-help@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.
