st: Generating new lines/record for groups of data

[Navid Asgari <navidstatalist@gmail.com>]

Hi all,

I would like to add new records to my data by groups. My longitudinal
data-set looks like this (the maximum length of a panel is 4
years[from 1990 to  1993, but some Firms have less observations, so I
have an unbalanced panel data])

Firm_ID      Year     var1   Var2
-------------------------------------------
G33            1990      2       2.5
G33            1991      3.4    1.2
G33            1992      5.6    2.8
G33            1993      8.1    9.2
KL1            1992      3       2.22


As you can see "G33" has three records from 1990 to 1993... Now I want
to make it look like a balanced panel data:

Firm_ID      Year     var1   Var2
-------------------------------------------
G33            1990      2       2.5
G33            1991      3.4    1.2
G33            1992      5.6    2.8
G33            1993      8.1    9.2
KL1            1992      3       2.22
KL1             1990     .         .
KL1             1991     .         .
KL1             1993     .         .


Thanks in advance!

Navid
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