Four years consecutive data

[Joska Pista]

Hi, i have a panel data with id and year between 1997-2003. I want to delete observations without four years consecutive data, the minimum number necessary to estimate the regression models. So that means that I want to keep for example this observation: 1997 1998 2000 2001 2002 2003 or 1998 1999 2000 2001 2003. But I want to delete the observation for example: 1997 2001 2002 2003 or 1997 1998 1999 2001 2002 2003. I hope someone can help me, it would be really important! Thank you!

[Nick Cox]

xtpatternvar (SSC) -- although a little out of date in a way that will not bite you -- can help here.

Here is a demonstration.

ssc install xtpatternvar 
webuse abdata, clear
xtpatternvar, gen(history)
tab history

    history |      Freq.     Percent        Cum.
------------+-----------------------------------
  ..1111111 |         14        1.36        1.36
  .1111111. |        273       26.48       27.84
  .11111111 |        152       14.74       42.58
  1111111.. |        434       42.10       84.68
  11111111. |         32        3.10       87.78
  111111111 |        126       12.22      100.00
------------+-----------------------------------
      Total |      1,031      100.00

In your case you are wanting to

keep if strpos(history, "1111")

as any four 1s in succession will suffice.