Read lines by number from a large file

Question

I have a file with 15 million lines (will not fit in memory). I also have a small vector of line numbers - the lines that I want to extract.

How can I read-out the l

Answer 1

If it's a binary file

Some discussion is here: Reading in only part of a Stata .DTA file in R

If it's a CSV or other text file

If they are contiguous and at the top of the file, just use the ,nrows argument to read.csv or any of the read.table family. If not, you can combine the ,nrows and the ,skip arguments to repeatedly call read.csv (reading in a new row or group of contiguous rows with each call) and then rbind the results together.