Dear R experts,
I am having difficulty using loops productively and would like to please
ask for advice.  I have a dataframe of ids and groups.  I would like to
break down the dataframe into groups, find the unique sets of ids, then
reassemble.  My thought was to use a loop, but I have been unable to finish
this loop in a logical way.  I would like to find the unique ids for group
1, group 2, etc., and rbind these back together.  However, I am unclear how
to do this because in other attempts my final product is always a part of
the last run loop.  My way of working around this has been to write.csv and
then re read at the end, which is so clumsy.  Previously, I have used a
store matrix for individual cells. 1. Is there a better way to approach
this?  2. How can I combine parts of matrices to other parts created in
prior loops?
I have created a primitive example below.  Each of the groups varies in
number, so my repetitive example below is not accurate.  In my real data,
ids repeat often within groups.
Thank you so much, Matt

example <- data.frame(id=rep(
( abs(round(rnorm(50,mean=500,sd=250),digits=0)))
,3), group=rep(1:15,10))
example <-example[with(example,order(id,group)),]

for (i in 1:15) {
ai <- example[example[,2]==i,][!duplicated ( example[example[,2]==i,][,1]
),]
write.csv(ai, paste('a',i,'.csv',sep=""))
}
b1<-read.csv('a1.csv')
b2<-read.csv('a2.csv')
b3<-read.csv('a3.csv')
b4<-read.csv('a4.csv')
b5<-read.csv('a5.csv')
b6<-read.csv('a6.csv')
b7<-read.csv('a7.csv')
b8<-read.csv('a8.csv')
b9<-read.csv('a9.csv')
b10<-read.csv('a10.csv')
b11<-read.csv('a11.csv')
b12<-read.csv('a12.csv')
b13<-read.csv('a13.csv')

unis2 <-
rbind(rbind(rbind(rbind(rbind(rbind(rbind(rbind(rbind(rbind(rbind(rbind
(b1,b2),b3),b4),b5),b6),b7),b8),b9),b10),b11),b12),b13)

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