1、gen where ="D" if foreign=="Domestic":origin
replace where ="F" if foreign=="Foreign":origin
如果foreign的值为domestic则where的值为D，否则where的值为F
2、显示自定义变量. list make foreign where
3、显示where变量的详细信息
4、定义model变量和modelwhere变量
gen model =usubstr(make,ustrpos(make,"")+1,.)
gen modelwhere =model +" " + where
5、显示model变量和modelwhere变量的值。
list make where model modelwhere
