麻烦高手帮忙看一下,错误在哪里。
- clear
- input id str2 ss year y
- 1 bg 2010 500
- 2 bh 2011 600
- 3 bg 2011 700
- 4 bp 2010 800
- 5 bp 2013 900
- 6 bh 2010 1000
- 7 bg 2012 1100
- 8 bp 2011 1200
- 9 bg 2013 1300
- 10 bp 2012 1400
- end
- foreach s in bp bg bh{
- foreach t in 2010 2011 2012 2013{
- preserve
- keep if ss=`s' & year==`t'
- save data`s'`t'
- restore
- }
-
- }
错误是:already preserved
r(621);
感激不尽!