R help - Jun 2010 - how to convert a set of strings to a list of unique numeric id?

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

Use a variable of class "factor"
> s <- c("ABCDDDD", "ACCDEDF", "ACCGEDF",
"ACCGEGF", "ACCDEDF", "ACCGEGF")
> fs <- factor(s)
> levels(fs)
[1] "ABCDDDD" "ACCDEDF" "ACCGEDF"
"ACCGEGF"
> unclass(fs)
[1] 1 2 3 4 2 4
attr(,"levels")
[1] "ABCDDDD" "ACCDEDF" "ACCGEDF"
"ACCGEGF"


On Sun, Jun 20, 2010 at 7:46 PM, G FANG <fanggangsw at gmail.com>
wrote:
> 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
>
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