R: Why is the [[ ]] approach for subsetting a list faster than using $?

Question

I\'ve been working on a few projects that have required me to do a lot of list subsetting and while profiling code I realised that the object[[\"nameHere\"]] approach to sub

Answer 1

Function [[ first goes through all elements trying for exact match, then tries to do partial match. The $ function tries both exact and partial match on each element in turn. If you execute:

system.time (
    for (i in 1:10000) {
     a.long.list[["something9973", exact=FALSE]]
     }
)

i.e., you are running a partial match where there is no exact match, you will find that $ is in fact ever so slightly faster.