Can anyone tell me how to find the common elements from multiple vectors?
a <- c(1,3,5,7,9)
b <- c(3,6,8,9,10)
c <- c(2,3,4,5,7,9)
I want to get the common elements from the above vectors (ex: 3 and 9)
c as variable name...
c(1,2...).
There might be a cleverer way to go about this, but
intersect(intersect(a,b),c)
will do the job.
EDIT: More cleverly, and more conveniently if you have a lot of arguments:
Reduce(intersect, list(a,b,c))
A good answer already, but there are a couple of other ways to do this:
unique(c[c%in%a[a%in%b]])
or,
tst <- c(unique(a),unique(b),unique(c))
tst <- tst[duplicated(tst)]
tst[duplicated(tst)]
You can obviously omit the unique calls if you know that there are no repeated values within a, b or c.
intersect_all <- function(a,b,...){
all_data <- c(a,b,...)
require(plyr)
count_data<- length(list(a,b,...))
freq_dist <- count(all_data)
intersect_data <- freq_dist[which(freq_dist$freq==count_data),"x"]
intersect_data
}
intersect_all(a,b,c)
UPDATE EDIT A simpler code
intersect_all <- function(a,b,...){
Reduce(intersect, list(a,b,...))
}
intersect_all(a,b,c)
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Reduceand the correct R capitalization!intersectis for set operations. If you have elements recurring in the vectors, you will lose this info because the vectors are turned into sets prior to intersect. E.g.intersect(c(1,1,2,3), c(1,1,3,4))would result inc(1,3), and you might have wanted the resultc(1,1,3).N <- max(unlist(L)); LT <- lapply(L, tabulate, nbins = N); v <- do.call(pmin, LT); unlist(sapply(1:N, function(x) rep(x, v[x])))Another way to do this would use thematchfunction along with negative subscripting to iteratively remove from each of the vectors every element added to the "kernel".