Adding month observations to year level data

[Adrienne Wold]

Hi,
I am working with the following variables:

* Example generated by -dataex-. For more info, type help dataex
clear
input float month double(year ID) float count
1 1990 7123 .
1 1991 7123 .
1 1992 7123 .
1 1993 7123 .
1 1994 7123 .
1 1995 7123 .
1 1996 7123 .
1 1997 7123 .
1 1998 7123 .
1 1999 7123 .
1 2000 7123 .
1 2001 7123 .
1 2002 7123 .
1 2003 7123 .
1 2004 7123 .
1 2005 7123 .
1 2006 7123 .
1 2007 7123 .
1 2008 7123 .
1 2009 7123 .
1 2010 7123 .
1 2011 7123 .
1 2012 7123 .
1 2013 7123 .
1 2014 7123 .
1 2015 7123 .
1 2016 7123 .
1 2017 7123 .
1 2018 7123 .
1 2019 7123 .
end

And I am trying to transform the structure such that each year has month observations from months 1-12. I tried the following code:

gen mdate = ym(year, month) 
format mdate %tm 
tsset ID  mdate
fillin ID mdate

but this only results in a missing mdate value and does not add the missing month observations. Is there another way to proceed here?

Thank you.

[Andrew Musau]

expand 12
bys year: replace month=_n