求助！关于retain语句！

shiyiming

<!-- s:o --><img src="{SMILIES_PATH}/icon_surprised.gif" alt=":o" title="Surprised" /><!-- s:o --> 小弟是初学者，有如下问题请教：
<!-- s:o --><img src="{SMILIES_PATH}/icon_surprised.gif" alt=":o" title="Surprised" /><!-- s:o --> 我想实现分组累计求和，写了如下语句：
data r2;
set r1;
by tag;
if first.tag then do;
retain tturn 0;
end;
tturn+turn;
run;

但在执行时retain语句总是保留了之前的值，而并没有置初值0，

请问我该如何实现？

shiyiming

[quote=&quot;hero&quot;:21da0]:o 小弟是初学者，有如下问题请教：
<!-- s:o --><img src="{SMILIES_PATH}/icon_surprised.gif" alt=":o" title="Surprised" /><!-- s:o --> 我想实现分组累计求和，写了如下语句：
data r2;
set r1;
by tag;
if first.tag then do;
retain tturn 0;
end;
tturn+turn;
run;

但在执行时retain语句总是保留了之前的值，而并没有置初值0，

请问我该如何实现？[/quote:21da0]
It's important to know that retain statement is non-executed statement and  the following code may solve your problem.
proc sort data=r1;
by tag;
run;
data r2
retain tturn;
set r1;
by tag;
if first.tag then tturn=0;
tturn+turn;
if last.tag then output;
run;

shiyiming

Please be noted that you should add a BY TAG after PROC SORT.

shiyiming

谢谢楼上的两位大哥! <!-- s:lol: --><img src="{SMILIES_PATH}/icon_lol.gif" alt=":lol:" title="Laughing" /><!-- s:lol: -->  <!-- s:lol: --><img src="{SMILIES_PATH}/icon_lol.gif" alt=":lol:" title="Laughing" /><!-- s:lol: -->