This is a common kind of question in data management, so you should
expect that -search- will turn up resources. Even if the keyword to
use in -search- is not evident, browsing the data management FAQs
reveals
FAQ . . . . . . . . . . . . . . . . . . . Number of distinct
observations
. . . . . . . . . . . . . . . . . . . . . . . N. J. Cox and
G. Longton
4/02 How do I compute the number of distinct observations?
http://www.stata.com/support/faqs/data-management/number-of-distinct-observations/
A general survey of counting distinct values is given in
SJ-8-4 dm0042 . . . . . . . . . . . . Speaking Stata: Distinct
observations
(help distinct if installed) . . . . . . N. J. Cox and G.
M. Longton
Q4/08 SJ 8(4):557--568
shows how to answer questions about distinct observations
from first principles; provides a convenience command
A .pdf is accessible at
http://www.stata-journal.com/sjpdf.html?articlenum=dm0042
Those surveys show several ways to approach this. Here is one:
egen tag = tag(country mfi year)
egen ndistinct = total(tag), by(country year)
In fact your example data suggest that
bysort country year : gen ndistinct2 = _N
would work too, but the first method is more general, just in case
there is a good reason for duplicates.
After that you just feed that variable within an expression for
weights to -regress-.
Nick
njcoxstata@gmail.com
On 25 April 2013 11:37, <ayayi@uqtr.ca> wrote:
- I have stata IC 10
-I have a panel data. To take in to consideration the considerable variation
of the MFIs (microfinance institutions) across countries on the empirical
results, I resort to a weighted least squares with the weight being the
inverse of the number of MFIs for the country in the database in a given
year.
Can someone help me on how to generate the inverse of the number of MFIs for
the country in the database in a given year and how to handle this WLS.
Please find below an example of the data
Thanks for your time and consideration
year mfi country
2004 AFS Afghanistan
2004 BRAC - AFG Afghanistan
2004 FINCA - AFG Afghanistan
2004 FMFB - AFG Afghanistan
2005 AFS Afghanistan
2005 BRAC - AFG Afghanistan
2005 CFA Afghanistan
2005 FINCA - AFG Afghanistan
2005 FMFB - AFG Afghanistan
2005 MADRAC Afghanistan
2004 ASC Union Albania
2004 BESA Albania
2004 FAF-DC Albania
2004 NOA - ALB Albania
2005 ASC Union Albania
2005 BESA Albania
2005 FAF-DC Albania
2005 NOA - ALB Albania
2004 BMM C rdoba Argentina
2004 Emprenda Argentina
2004 Entre Todos Argentina
2004 FIE Gran Poder Argentina
2004 Grameen Chaco Argentina
2005 Alternativa 3 Argentina
2005 BMM C? rdoba Argentina
2005 Emprenda Argentina
2005 Entre Todos Argentina
2005 FIE Gran Poder Argentina
2005 Grameen Chaco Argentina
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