各位老师好，
我写了一个logistic回归程序如下：

proc logistic data=Ads.f_case1_c descending;
class lenert_eight (param=ref ref='State 8') gender (param=ref ref='Female');
model GP_C (event='Yes')=age gender lenert_eight / stb aggregate; * stb: display the standardized estimates, aggregate: calculate deviance and Pearson goodness-of-fit statistics ;
by lenert_eight;
output out=GP_C_pro  predicted=prob ;
format gender gender. GP_C GP_C. lenert_eight lenert_eight.;
run;

但是进行到by lenert_eight的时候程序提示出错：ERROR: Data set ADS.F_CASE1_C is not sorted in ascending sequence. The current BY group has Lenert 8 states = State 1 and the next BY  group has Lenert 8 states = ..


即使改成 by lenert_eight descending 或者 by lenert_eight notsorted都不行。求教到底是怎么回事？怎么解决？