Efficient alternatives to merge for larger data.frames R

Question

I am looking for an efficient (both computer resource wise and learning/implementation wise) method to merge two larger (size>1 million / 300 KB RData file) data frames.

Answer 1

Here are some timings for the data.table vs. data.frame methods.
Using data.table is very much faster. Regarding memory, I can informally report that the two methods are very similar (within 20%) in RAM use.

library(data.table)

set.seed(1234)
n = 1e6

data_frame_1 = data.frame(id=paste("id_", 1:n, sep=""),
                          factor1=sample(c("A", "B", "C"), n, replace=TRUE))
data_frame_2 = data.frame(id=sample(data_frame_1$id),
                          value1=rnorm(n))

data_table_1 = data.table(data_frame_1, key="id")
data_table_2 = data.table(data_frame_2, key="id")

system.time(df.merged <- merge(data_frame_1, data_frame_2))
#   user  system elapsed 
# 17.983   0.189  18.063 


system.time(dt.merged <- merge(data_table_1, data_table_2))
#   user  system elapsed 
#  0.729   0.099   0.821