[R] algorithm to create unique identifiers

[Henrik Bengtsson]

On Thu, Sep 4, 2008 at 8:44 PM, Ralph S. <ruffel1 at hotmail.com> wrote:
>
> Hi all,
>
> I am trying to create a unique identifier for each row, combining numbers from three columns.
>
> Do you know if there is a general formula to do this (or some manual where I can read about this)?
>
> I figure I can use the numeric entries of the columns as "coordinates" and multiply them with different coefficients (different magnitudes) to get the unique ID - but it would be nice to read about such algorithms in general.

What are you numbers?  Are they in a fixed range?  Integers or reals?
If fixed range integers, it is easy.  Think regular numerical
representation, e.g. binary, octadecimal, decimal and hexadecimal.

For a more generic solution that works with any data types, see e.g.
MD5 [http://en.wikipedia.org/wiki/MD5].  It is not guaranteed to
generated unique codes, but it is extremely rare that two different
inputs gives the same MD5 code.  MD5 (and others) are implemented in
the 'digest' packages, e.g.

> library(digest)
> digest(list(a=1, b=list(1:10, c=letters)))
[1] "73e0ae066a97bfff7f79d41c65b55fde"

My $.02

/Henrik


>
> Any links/input would be great -
>
> Ralph
>
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