select_cols 里面好像没有解析那个 i，出来的结果不符合预期
select_cols = (); for (i in 0..(dim-1)) { select_cols.append!(sqlColAlias(<sum(class==i)/float(T)>, "L_"+string(i))); } print(select_cols) res = sql(select=select_cols, from=dt_Nth, groupBy=sqlCol("code")).eval()
用each动态对元代码中的变量赋值
dim=10 T=1000 select_cols=each(def(x,T):sqlColAlias(<sum(class==x)\float(T)>,"L_"+string(x)),0..(dim-1),take(T,dim))
