topic SAS 7613130380 - Lesson 4 - Why the keep statement is before IF-Then statement? in Programming 1 and 2

SAS 7613130380 - Lesson 4 - Why the keep statement is before IF-Then statement?

GN0001 — Wed, 22 Jul 2020 03:39:53 GMT

Hello team,

I have this code:

data storm_cat;
    set pg1.storm_summary;
    keep Name Basin MinPressure StartDate PressureGroup;
    *add ELSE keyword and remove final condition;
    if MinPressure=. then PressureGroup=.;
    else if MinPressure<=920 then PressureGroup=1;
    else PressureGroup=0;
run; 

PressureGroup is created after the keep statement. How does keep statement knows about
PressureGroup?

Your response is greatly appreciated.
GN

Re: SAS 7613130380 - Lesson 4 - Why the keep statement is before IF-Then statement?

ballardw — Wed, 22 Jul 2020 04:18:30 GMT

@GN0001 wrote:

Hello team,

I have this code:

data storm_cat;
    set pg1.storm_summary;
    keep Name Basin MinPressure StartDate PressureGroup;
    *add ELSE keyword and remove final condition;
    if MinPressure=. then PressureGroup=.;
    else if MinPressure<=920 then PressureGroup=1;
    else PressureGroup=0;
run; 

PressureGroup is created after the keep statement. How does keep statement knows about
PressureGroup?

Your response is greatly appreciated.
GN

There are statements that SAS refers to as "Declaritive".

Declarative statements supply information to SAS and take effect when the system compiles program statements.

The order of most of these does not matter though the position may look "odd" in some contexts, especially if you get in a particular coding habit. Exceptions are Data (start a data step) Cards/Cards4/Datalines/Datalines4 which precede in-line data at the end of a step, and the End which ends a DO or Select block. Length may go anywhere but could generate some warnings about variables that exist.

Declarative Statements

ARRAY

DATALINES4

Labels, Statement

ATTRIB

DROP

LENGTH

BY

END

RENAME

CARDS

FORMAT

RETAIN

CARDS4

INFORMAT

WHERE

DATA

KEEP

WINDOW

DATALINES

LABEL

Declarative Statements
ARRAY	DATALINES4	Labels, Statement
ATTRIB	DROP	LENGTH
BY	END	RENAME
CARDS	FORMAT	RETAIN
CARDS4	INFORMAT	WHERE
DATA	KEEP	WINDOW
DATALINES	LABEL

Re: SAS 7613130380 - Lesson 4 - Why the keep statement is before IF-Then statement?

Kurt_Bremser — Wed, 22 Jul 2020 04:54:04 GMT

The keep statement controls what goes to the output dataset(s). It has no effect on the presence of variables within the data step.

Re: SAS 7613130380 - Lesson 4 - Why the keep statement is before IF-Then statement?

Cynthia_sas — Wed, 22 Jul 2020 14:25:09 GMT

Hi:
Please go back and review the videos that talk about the KEEP and DROP statements. The KEEP statement is setting a flag at compile time that tells SAS which variables need to be sent to the output dataset -- in this case, WORK.STORM_CAT. The variables you list in the KEEP or DROP statement can come from either the INPUT dataset (PG1.STORM_SUMMARY) or the OUTPUT dataset (WORK.STORM_CAT) or you can list variables that you create in the DATA step, (such as PressureGroup).

Order of the KEEP statement in the program does not matter. The program would work the same way no matter where the KEEP statement was positioned. We recommend putting "housekeeping" statements at the top of the program, but some people are in the habit of putting them at the bottom. It doesn't matter -- KEEP, DROP or WHERE statements can be positioned anywhere in a DATA step program.

Cynthia