程序如下：tw (line y1,yaxis(1) ytitle(district GDP（100million）)）（line y2,yaxis(2) ytitle(SO2 output（tons)) ‖,ylabel(3700(1000)26300),axis(1) ylabel(52500(20000)1300000) x xtitle(year) xlabel(1999(1)2013) legend(off) title("homework") subtitle（"Sichuan 1999-2013") note（"source：四川统计年鉴")