match two columns with two other columns

Question

I have several rows of data (tab separated). I want to find the row which matches elements from two columns (3rd & 4th) in each row with two other colum

Answer 1

DWin's answer is solid, however with large-ish arrays, typically over 50k or so you'll run into memory issues, as the matrices you're creating are huge.

I'd do something like:

match(
  interaction( indat$V3, indat$V10),
  interaction( indat$V4, indat$V11)
);

Which concatenates all the values of interest into factors and does a match.

This is a less pure solution, but faster/more manageable.