怎么理解 'if _n_=1 then set abc;'

shiyiming

最近看到一个code：
data a;
  if _n_=1 then set b;   /*or if 0 then data b;*/
. . .
run;
怎么理解这个condition statement?
等同于data a; set b; run;?

thx!!!

shiyiming

just mean only at the first iteration (where the automatic variable _n_ is 1), copy variable (and value) from data set abc.  Note the value will be retained.

Compare with the following:
If 0 then set abc;             /*only copy variables, but no value*/

shiyiming

got you, thanks a lot!

sunnyswing

shiyiming 发表于 2013-12-27 02:39
just mean only at the first iteration (where the automatic variable _n_ is 1), copy variable (and va ...

I have the same question. But just look at here " Note the value will be retained.".How to maintain the value is not retained, as I just want one record from data set "abc"?

davyin

  GOT IT

gogotiger

I got duplicates when I tried the following:
data a; if _n_=1 then set sashelp.class;  run;

anyone can help? Thx!!!!

bird

gogotiger 发表于 2014-5-13 05:08
I got duplicates when I tried the following:
data a; if _n_=1 then set sashelp.class;  run;

data a;
  if _n_ = 1 then set abc;
  else stop;
run;

gogotiger

thxs bird!

berry_li

bird好像是我吧。。。我了个去。。。