search for: accgedf

Hi, I have been a matlab user and is learning R. I want to convert a large list of strings to a list of unique numeric ids to reduce storage space. For example, there is a string list (there are duplicates) ABCDDDD ACCDEDF ACCGEDF ACCGEGF ..... ACCDEDF ACCGEGF and I want to have a corresponding numeric id list 1 2 3 4 .... 2 4 In matlab, the 'unique' function can do this in addition to give the unique set, but in R, 'unique' only gives the unique set Please advice me on this. Thanks, Gang