Using Proc Datasets for Efficiency

Originally presented as a Coder’s Corner @ NESUG2000 by

Ken Friedman

Reviewed by Karol Katz

Proc Datasets, an Overview Used to manage SAS Datasets List,change, append and repair datasets Create and maintain indexes Proc DATASETS includes all capabilities of the

APPEND, CONTENTS and COPY procedures Procedure commands execute with a RUN

command or another DATASETS command The procedure remains active until another

procedure, dataset statement, or QUIT command is executed

LIBNAME input ‘SAS-data-library’ ;PROC DATASETS LIBRARY = input ;DATASETS commandsRUN;

APPEND vs SET SET command reads ALL observations from the

datasets being concatenated. The APPEND command ONLY reads the

observations from the dataset being appended. If the two datasets do not contain the same

variable names, types or lengths, you can use the FORCE option to force the append to take place.

APPEND vs. SETPROC DATASETS; APPEND OUT = membr_b DATA = Membr_a (WHERE = (year=2004)); QUIT; RUN;

DATA membr_b;

SET membr_b membr_a

(WHERE = (year=2004));

RUN;

CHANGE Command Used to rename one or more members within a

SAS library Specify old name on left of the equals sign and

new name on right The following example renames two temporary

datasets

PROC DATASETS ;

CHANGE temp1 = Jan_Mar04

temp2 = Apr_Jun04;

RUN;

Copy command To copy or move a SAS a member from one

library to another To limit copying to specific members use either

SELECT or EXCLUDE options To move a member from one library to another

and then delete the original member, use the MOVE option

LIBNAME lib1 ‘SAS-data-library1’;

LIBNAME lib2 ‘SAS-data-library2’;

PROC DATASETS;

COPY in = lib1 out = lib2 MOVE;

SELECT member1 member2; * / memtype = (data);

RUN;

Modify Command Works only on one dataset at a time Allows you to change or specify formats,

informats, and labels, rename variables and create and delete indexes

For an existing dataset the MODIFY command is the best way to make changes because no observations are read in or written out during processing

Using a data step with a set statement you can also make changes, however all oberservations are read in & written out. In a large dataset time and storage can be significant

MODIFY Example:LIBNAME input ‘SAS-data-library’ ;PROC DATASETS LIBRARY = input ; MODIFY income(LABEL=‘Household Income’); RENAME oldvar=newvar; LABEL newvar=‘originally called old’; FORMAT income comma11.2; RUN;

DATASETS procedure is interactive Commands execute immediately in the

order they appear Be cautious when working with this

procedure