做了下面的do命令
xtset city year
gen year14=1 //政策在2014年实行
replace year14=0 if year<=2014
gen yuebei=0 //政策中,粤北包括韶关、梅州、清远、河源、云浮
replace yuebei=1 if city==440200|city==441400|city==441600|city==441800|city==445300
gen yuebei_yr=yuebei*year14 //生成粤北和时间的交互项
gen zhu=0 //政策中,珠三角包括广州、深圳、珠海、佛山、江门、东莞、中山、惠州、肇庆
replace zhu=1 if city==440100|city==440300|city==440400|city==440600|city==441300|city==440700|city==441900|city==442000|city==441200
gen zhu_yr=zhu*year14 //生成珠三角和时间的交互项
gen yuedongxi=0 //政策中,粤东包括汕头、汕尾、潮州、揭阳,粤西包括湛江、阳江、茂名
replace yuedongxi=1 if city==440800|city==440900|city==441700|city==440500|city==441500|city==445100|city==445200
gen yuedongxi_yr=yuedongxi*year14 //生成粤东西和时间的交互项
gen treated=0 //粤北为参照组,粤东西和珠三角地区是实验组
replace treated=1 if city==440800|city==440900|city==441700|city==440500|city==441500|city==445100|city==445200|city==440100|city==440300|city==440400|city==440600|city==441300|city==440700|city==441900|city==442000|city==441200
reg water yuebei zhu yuebei_yr zhu_yr year14 i.city i.year,r
reg gas yuebei zhu yuebei_yr zhu_yr year14 i.city i.year,r
reg dust yuebei zhu yuebei_yr zhu_yr year14 i.city i.year,r
//DID回归
reg water yuebei yuedongxi yuebei_yr yuedongxi_yr year14 i.city i.year,r
reg gas yuebei yuedongxi yuebei_yr yuedongxi_yr year14 i.city i.year,r
reg dust yuebei yuedongxi yuebei_yr yuedongxi_yr year14 i.city i.year,r
//DID回归
得到了下面的结果 所以回归分析的结果应该是
政策对粤东西地区的dust、gas和water显著有效,对珠三角的dust/gas/water是没有效果的?