Jeanna -
I can't imagine how you could solve this problem with a
loop, but here's one way to solve it using R:
First, I'll create a data frame with a family variable:
x = data.frame(family = rep(1:20,sample(2:5,20,replace=TRUE)))
Next, I'll number each family member within each family:
x$seq = ave(x$family,x$family,FUN=seq)
Now I'll choose a random number within each family:
x$use = ave(x$family,x$family,FUN=function(x)sample(1:length(x),1))
Finally, I'll select the family member whose sequence number
matches the random number:
answer = subset(x,seq == use)
Hope this helps. Take a look at the help page for the ave function
to understand how it works.
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Tue, 24 May 2011, Jeanna wrote:
I have a data table with one column that indicates families, and subsequent
columns with other characteristics. I want to randomize one member of the
family to a separate table. My approach is to count the number of members,
set up a random number generator, and assign the family member based on
where they fall within the random number spectrum.
Is there a way to count the number of family members as I loop through the
whole table?
Something like this:
for (j in 1:15){
if (x$family[j] == x$family[j+1]){
count = count +1
(which doesn't work)
as I do the larger:
for (i in 2:nrow(x.tab)){
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