ben.powell@CLA.CO.UK (Ben Powell) wrote in message news:<200309251339.h8PDd3v01281@listserv.cc.uga.edu>... > I'm not clear on what can be done in any single datastep and would > appreciate any pointers. > > Say for example I want to copy a dataset to my work lib, rename a variable > and keep that and one other variable. Because in the past I have found that > sometimes a step won't action unless there is a run command after it I > would break this job into 3 seperate data steps, which is quite repetative. > Is there a rule of thumb for when a new datastep is needed and how many > steps can be included in a datastep? > > e.g. > > data a; > set lib.a;run; > data a (rename=(var1=var2)); > set a;run; > data a; > set a; > keep var2 var3; > run;

Hi Ben,

It seems that there's a misunderstanding of the data step at work here. Reading any good SAS Data Step programming manual will help; in the mean time, perhaps it will help to note a couple properties of the data step:

* Each data step is a separate program; it is compiled and executed separately from every other step in your SAS job. Thus, once you start thinking of the data step as a separate program in its own right, you can start to exploit its tremendous power.

* Each data step is an implicit loop. A SAS Data Step manual will explain A LOT about this fundamental concept.

In the meantime, other posters solved your problem using data set options. To give you some further insight, the same thing could be accomplished with:

data a; set lib.a (rename (var1=var2)); keep var2 var3; run;

Picture the above data step as a loop, each iteration reading in one observation from lib.a (via the set statement) and simultaneously renaming var1 to var2, then outputting only var2 and var3. You can do a tremendous amount of other processing in this implicit loop; each iteration of the loop will carry out the processing on just the current observation.

I hope that helps, Matt