[R] how to convert a set of strings to a list of unique numeric id?

[G FANG]

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