求助各位大神：以下数据，想要计算每年的前五年间，ipc_3的非重复值的数量，比如2002年即统计1998-2002年间icp_3的非重复值数，是1，2003年统计1999-2003年间，是1，以此类推，2004年是1，2005年是6，2006年是9.
尝试了rangestat,rangerun,都没有成功。求教代码应该如何编写？万分感谢！
clear
input str6 stkcd str4 year str3 ipc_3
"000002" "1992" ""   
"000002" "1993" ""   
"000002" "1994" ""   
"000002" "1995" ""   
"000002" "1996" ""   
"000002" "1997" ""   
"000002" "1998" ""   
"000002" "1999" ""   
"000002" "2000" ""   
"000002" "2001" ""   
"000002" "2002" "E04"
"000002" "2003" ""   
"000002" "2004" "E04"
"000002" "2004" "E06"
"000002" "2004" "A47"
"000002" "2005" "E05"
"000002" "2005" "E06"
"000002" "2005" "F23"
"000002" "2005" "E04"
"000002" "2005" "A01"
"000002" "2006" "A47"
"000002" "2006" "B65"
"000002" "2006" "D06"
"000002" "2006" "E04"
"000002" "2006" "A01"
"000002" "2006" "E03"
end