sas 怎么另变量自动等于下一个观测值,类似于next方法

data zhuangtai1;
set zhuangtai(drop = roles serial_number);
by userid;
format valid_from_dt valid_to_dt yymmdd10.;
retain valid_to_dt 0;
valid_from_dt = trade_date;
if last.userid = 1 then do;
valid_to_dt = "31dec9999"d;
end;
else if last.userid ~= 1 then do ;
valid_to_dt = ;
end;
label userid = '用户编号' trade_status = '交易状态' trade_date = '交易日期'
lkh = '开户' lcz = '充值' ltb = '投标' ltx = '体现' lzqzr = '债券转让' ;
run;

用宏命令实现

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