data.frame slicing - string

Question

I hope this question is not too simple for this board.
I have created a data.frame df:
CAS Name CID
89 13010-47-4 Lomustine 3950
90 130209-82-4 Latanoprost 5311221,5282380,46705340,3890
91 130636-43-0 Nifekalant 268083
92 130929-57-6 Entacapone 5281081
and a vector vec
[1] 5282380 18471829 45923789 44308022 44266812 24883465 24867475 24867460
I would like to extract the rows of df which contains any number of vec. I tried to solve this problem by this code:
df$GC[(df$CID %in% vec)] = 1
df[df$GC==1,]
But the problem with this solution is, that I only get the rows, which contain only one number in the CID column. Rows which contain several values in CID like line 90 do not appear.
Is there an elegant solution for this problem?
Thanks in advance

Answer 1

Given your comment on EDi's answer (which I like) I thought I'd make a suggestion.
Squeezing comma separated values into a single column of a data frame is awkward and (in my experience) just leads to frustration. I often find it simpler to keep it in a separate data structure, a list:
dat <- read.table(text = " CAS Name CID
13010-47-4 Lomustine 3950
130209-82-4 Latanoprost 5311221,5282380,46705340,3890
130636-43-0 Nifekalant 268083
130929-57-6 Entacapone 5281081",sep = "",header = TRUE)
cid <- sapply(dat$CID,strsplit,",",USE.NAMES = FALSE)
In this form, things are often easier to work with:
ID <- c(5282380, 18471829, 45923789, 44308022, 44266812, 24883465, 24867475, 24867460, 3950)
dat[sapply(cid,function(x) {any(x %in% as.character(ID))}),]
CAS Name CID
1 13010-47-4 Lomustine 3950
2 130209-82-4 Latanoprost 5311221,5282380,46705340,3890
You can always use rownames in dat and the names of the list to keep each item straight, if you're worried about orderings changing.
(Also note that my anonymous function is assuming that ID will be found eventually by R's scoping rules; you can alter the function to pass in ID explicitly if you like.)

Answer 2

One way is to use grep():
> txt <- " CAS Name CID
+ 13010-47-4 Lomustine 3950
+ 130209-82-4 Latanoprost 5311221,5282380,46705340,3890
+ 130636-43-0 Nifekalant 268083
+ 130929-57-6 Entacapone 5281081
+ "
> con <- textConnection(txt)
> df <- read.table(con, header = TRUE)
> close(con)
> ID <- c(5282380, 18471829, 45923789, 44308022, 44266812, 24883465, 24867475, 24867460, 3950)
> grep(paste("\\b", ID, "\\b", sep="", collapse = "|"), dat$CID)
[1] 1 2