请教logistic回归sas哑变量设置程序

webgu 发表于 2012-5-5 22:20
data dstst;
  set dstst;
dum1=(smoking=1);/*1为不吸烟*/

data dstst;
  set dstst;
dum1=(smoking=1);/*1为不吸烟*/
dum2=(smoking=2);/*2为偶尔吸烟*/
run;

data dstst;
  set dstst;
dum1=(smoking=2);/*2为偶尔吸烟*/
dum2=(smoking=3);/*3为经常吸烟*/
run;
data dstst;
  set dstst;
dum1=(smoking=1);/*1为不吸烟*/
dum2=(smoking=3);/*3为经常吸烟*/
run;
三者有什么区别呢  怎么选择啊  求解

proc logistic ...; class smoke (param=ref ref=‘0’);/*哑变量：把0设为对比组*/ model ... ... ...run;

用class ref时，默认ref=last,如果想用第一组作为参考组，需加入ref=first