Thoughts for faster indexing
Neal Fultz <nfultz <at> gmail.com> writes:
Noah, If N is # of rows, k is # of unique IDs Using which() is O(N), using which() in a loop is going to be O(Nk); sorting the entire data is O(N ln N) and then you can process it in contiguous blocks, no which required. -Neal
You might also take a look at the 'dplyr' package on Github: it's next-gen plyr, engineered for performance ... https://github.com/hadley/dplyr