[R] Putting x into the right subset

Uwe Ligges ligges at statistik.uni-dortmund.de
Sat Jul 22 11:45:36 CEST 2006

John Wiedenhoeft wrote:

> Dear all,
> I'm sorry I have to bother you with this newbie stuff.
> Within a loop I obtain pairs of values x <- c(a, b). An empty set M is
> defined before the loop (as a list or whatever). Now I want to do the
> following: if there is a vector y in M  that contains at least one of
> the values of x, then x shall be concatenated to y. If y doesn't contain
> any of the values in x, then x shall be put into M as a new vector. I
> first imagined it to be trivial but I'm having a hard time with the
> if-statement. I tried to define a function contains(value, vector),
> which returns FALSE or TRUE, but R complains that I tried to execute a
> "non-function"...
> Could anybody help a despaired newbie, please!

Example (maybe not efficient, but should do the trick):

M <- list()
temp <- NA
for(i in 1:20){
     a <- sample(1:10, 1)
     b <- sample(11:20, 1)
     x <- c(a, b)
     if(i > 1)
         temp <- which(sapply(M, function(y) any(x %in% y)))[1]
         M[[temp]] <- c(M[[temp]], x)
         M[[length(M) + 1]] <- x

> Thanks a lot,
> John
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