I have a panel data like this :
year ID S(t)
2008 N987 S1234
2009 N987 S8875
2010 N987 S7465
2008 E867 F8402
2009 E867 S1234
2010 E867 R9879
2011 E867 Q8687
2012 E867 F8687
2013 E867 J8687
I want,
year ID S(t) S(t-1)
2008 N987 S1234 0
2009 N987 S8875 S1234
2010 N987 S7465 S8875
2008 E867 F8402 0
2009 E867 S1234 F8402
2010 E867 R9879 S1234
2011 E867 Q8687 R9879
2012 E867 F8687 Q8687
2013 E867 J8687 F8687
But I have 304429 different ID's, and the Panel is not ordered by year and id.
Can someone please help me?
Thank you!