R matching more than 2 conditions and return the response value

Question

Hi I have two data set where the first one is a set of index:

ind1<-rep(c(\"E\",\"W\"), times=20)
ind2<-sample(100:150, 40)
y<-c(1:40)
index<-dat         


        

Answer 1

merge(data, index, by.x=c("ind1", "ind2"), by.y=c("x1", "x2"), all.x=TRUE, all.y=FALSE)

will give you the x and y values for each matching combination of ind1 and ind2, and x1 and x2. All combinations of x1 and x2 will be kept (even if that combination of ind1 and ind2 doesn't occur in index, but combinations of ind1 and ind2 that don't occur in data will be dropped. As written, the solution will keep x3 and y values, but if you'd like to drop the y values you can use merge(data[ ,-3], ... as per @Ferdinand.kraft 's suggestion.