I have two csv files, and each of which consists of one column of data
For instance, vecA.csv is like
id
1
2
vecB.csv is like
id
3
2
I read the data set as follows:
vectorA<-read.table("vecA.csv",sep=",",header=T)
vectorB<-read.table("vecB.csv",sep=",",header=T)
I want to generate a vector consisting of elements belonging to B only.
You are looking for the function setdiff
setdiff(vectorB$id, vectorA$id)
If you did not want this reduced to unique values, you could create a not in function
(kudos to @joran here Match with negation)
'%nin%' <- Negate('%in%')
vectorB$id[vectorB$id %nin% vectorA$id]
If your vector's are instead data.tables, then all you need are five characters:
B[!A]
library(data.table)
# read in your data, wrap in data.table(..., key="id")
A <- data.table(read.table("vecA.csv",sep=",",header=T), key="id")
B <- data.table(read.table("vecB.csv",sep=",",header=T), key="id")
# Then this is all you need
B[!A]
[Matthew] And in v1.8.7 it's simpler and faster to read the file as well :
A <- setkey(fread("vecA.csv"), id)
B <- setkey(fread("vecB.csv"), id)
B[!A]
