求教一个编程小问题

shiyiming

有一个数据库格式如下
id     time     m
1      5         6
1      12       8
1      17       8
2      3         3
2      8         2
2      10       1
……
如何把每个id中time最大的观测值提取出来
（即是：id为1选中time17那个值；id为2的选中time为10的）

shiyiming

proc sort data = work.a out = work.b;
by id;
run;
proc means data = work.b max;
var time;
class id;
run;

shiyiming

[code:24017]proc sql;
create table maxtime as
select id, max(time) as maxtime
from a
group by id;
quit;[/code:24017]

shiyiming

proc sort data=a;
by id;
data b;
set a;
by id;
if last.id;
run;

this method can't handle with the dataset in which variable have two same max value.

shiyiming

那就综合一下，把所有最大记录保存下来
proc sort data=a;
   by id descending time;
data b;
  retain max;
  set a;
  by id;
  if first.id then do;
    max=time;
        output;
  end;
  else
    if time=max then output;
  drop max;
run;

shiyiming

我这边不能试,这个可能更简洁点
[code:b042b]proc sort data=a;
by id descending time;
data b;
set a;
by id;
if first.id or time=lag(time);
run;[/code:b042b]

shiyiming

可以运行，的确要简洁些

shiyiming

谢谢大家，问题解决^_^

shiyiming

[quote="yooyork":46d54]
......
[color=red:46d54]by id;[/color:46d54]
......
[/quote:46d54]

应该是
[code:46d54]proc sort data=a;
by id time;
data b;
set a;
by id;
if last.id;
run;[/code:46d54]

shiyiming

哦，是的，疏忽了 ：）