I don't see your point...
In your case ndigits is 0 and therefore: 

unique = region * 10 + sector 

This is enough to produce unique values for each region/sector
combination.
(1,2) and (2,1) must be treated as different and they do...

On Thu, 2013-11-21 at 15:57 +0100, Pindar wrote:

Yes, nice, but one has to check that 'region' and 'sector' do not
share a common cluster ID like in

<hansl> 
region = randgen(i,1,10) 
sector = randgen(i,1,5) 
<hansl> 

Since combinations like (1,2) and (2,1) are treated as being
different.
Hence, with a primary data manipulation 'sector = randgen(i,1,5) +100'
things should be fine.

21.11.2013 15:13, Riccardo (Jack) Lucchetti:

On Thu, 21 Nov 2013, Giuseppe Vittucci wrote: 

Hi, 

I have firm level data and two categorical variables (region and 
sector). 
I need to define another variable which is an index identifying
the 
unique combinations region-sector each firm belongs to, so I can
use it 
in computing cluster-robust s.e. 

One way to do this is to use the command "values" for region and
sector 
and then use a nested loop, but this seems quite
time-consuming... 

Is there a simpler way in gretl to do it? 

You mean, like this? 

<hansl> 
nulldata 1024 

# simulated data 
region = randgen(i,1,20) 
sector = randgen(i,10,99) 
# ---------------------------------------------- 
scalar ndigits = floor(log10(max(sector))) 
series unique = region * 10^(ndigits+1) + sector 
</hansl> 


------------------------------------------------------- 
  Riccardo (Jack) Lucchetti 
  Dipartimento di Scienze Economiche e Sociali (DiSES) 

  Università Politecnica delle Marche 
  (formerly known as Università di Ancona) 

  r.lucchetti@univpm.it 
  http://www2.econ.univpm.it/servizi/hpp/lucchetti 
-------------------------------------------------------


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