st: a variable is decreased by 1 ?

[Gijs Dekkers <gd@plan.be>]

Dear fellow Stata-users,

I really would appreciate some help with this strange problem...

I have a panel dataset, with the individual number 'pid' and the year 
variabele 'jaar'. The variable pidnew is an alternative 
individual-identification number. This variabel, and 'jaar' don't really 
do anything, but I include it to show that the individual does not 
changes in what follows.

So, the starting dataset is:

. list pid pidnew jaar if (pid==17025101 & jaar==2002)

           +--------------------------+
            |      pid       pidnew   jaar  |
            |--------------------------|
10597. | 17025101       62   2002 |
           +--------------------------+

So this is the data line of individual 17025101 in the year 2002. Now I 
create a copy ('pidold') of this individual identification number,

. gen pidold = pid

. list pid pidold pidnew jaar if (pid==17025101 & jaar==2002)

           +-------------------------------------+
            |      pid         pidold       pidnew   jaar |
            |-------------------------------------|
10502. | 17025101   1.70e+07       62   2002 |
           +-------------------------------------+

The resulting variable is difficult to read, for it is in the scientific 
notation. So I change the format...

. format pid pidold epid %14.0f 
. list pid pidold pidnew jaar if (pid==17025101 & jaar==2002)

           +-------------------------------------+
           |      pid         pidold           pidnew   jaar |
           |-------------------------------------|
10597. | 17025101   17025100       62   2002 |
           +-------------------------------------+

And all of a sudden, the variabele 'pidold', which is supposed to be 
equal to 'pid' has decreased by one! Or, which is more likely, the 'gen 
pidold = pid' has not done what it should have done, because the format 
of pidold was set so that information was lost. However, I cannot set a 
format of a variable prior to its existence.

I have also tried juggling with 'recast' and different formats, but 
nothing seems to help.

I would really appreciate your help in finding a solution!

Gijs







--
Gijs Dekkers
Attach� Federal Planning Bureau
Research fellow CESO, Katholieke Universiteit Leuven
Kunstlaan 47-49 Avenue des Arts
1000 Brussels, Belgium
phone ++32/(0)2/5077413
fax  7373
skype gdekkers2209
gd@plan.be, gijs.dekkers@soc.kuleuven.be



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