Introduction to Data Set Options Mark Tabladillo, Ph.D. Software Developer, MarkTab Consulting...

Introduction to Data Set Options

Mark Tabladillo, Ph.D.Software Developer, MarkTab ConsultingAssociate Faculty, University of Phoenix

January 30, 2007

Introduction

• Data set options allow features during dataset processing

• Most SAS data set options can apply to either input or output SAS data sets in DATA steps or procedure (PROC) steps

• Data set options allow the data step to control variables, observations, security, and data set attributes

Outline

• Define data set options

• Provide examples in four categories

• Discuss data set processing rules

Definition

• Data set options specify actions that apply only to the SAS data set with which they appear.

http://support.sas.com/onlinedoc/913/getDoc/en/lrcon.hlp/a002612367.htm

Syntax

• Specify a data set option in parentheses after a SAS data set name. To specify several data set options, separate them with spaces.

(option-1=value-1<...option-n=value-n>)


Outline




Quick Examples

• Data set options enable us to perform operations such as these:– Renaming variables– Selecting only the first or last n observations

for processing– Dropping variables from processing or from

the output data set– Specifying a password for a data set– Adding dataset labels


Common Option Categories

• Variable Control

• Observation Control

• Security

• Data Set Attributes

Examples Datasetdata work.sales (drop=i randomState);

length state $2 sales 8 randomState 3;do i = 1 to 2500;

randomState = round(rand('gaussian',3,1)+0.5);if randomState in (1,2,3,4,5) then do;

select(randomState);when(1) state='TN';when(2) state='AL';when(3) state='GA';when(4) state='FL';when(5) state='MS';

end;sales = int(rand('gaussian',1000000,500000));output work.sales;

end;end;run;

List of Common Options

http://support.sas.com/onlinedoc/913/getDoc/en/lrdict.hlp/a000104210.htm

SAS Data Set Option

Description

Variable Control

DROP= Data Set Option

Excludes variables from processing or from output SAS data sets

KEEP= Data Set Option

Specifies variables for processing or for writing to output SAS data sets

RENAME= Data Set Option

Changes the name of a variable

Examples: Variable Control

data work.salesReformat;set work.sales (drop=sales);run;

data work.salesReformat2;set work.sales (keep=state);run;

proc sort data=work.sales (rename=(state=salesState)) out=work.salesReformat3 (drop=sales);by salesState;run;



SAS Data Set Option

Description

Observation Control

FIRSTOBS= Data Set Option

Specifies which observation SAS processes first

IN= Data Set Option Creates a variable that indicates whether the data set contributed data to the current observation

OBS= Data Set Option Specifies when to stop processing observations

WHERE= Data Set Option

Selects observations that meet the specified condition

Examples: Observation Control* (obs - firstobs) + 1 = results; data work.selectObs1;

set work.sales (firstobs=1 obs=200);run;

data work.selectObs2;set work.sales (firstobs=200 obs=400);run;

proc print data=work.sales (obs=25);run;

proc freq data=work.sales (firstobs=1);tables state;run;

proc means data=work.sales (obs=max);class state;var sales;run;

Examples: Observation Control

data work.combineObs1;set work.selectObs1 (in=in1) work.selectObs2 (in=in2);length source $12;if in1 then source = 'Dataset One';else if in2 then source = 'Dataset Two';run;

data work.combineObs2;set work.selectObs1 (in=in1) work.selectObs2 (in=in2);if in1 and in2 then output;run;



SAS Data Set Option Description

Security ALTER= Data Set Option Assigns an alter password to a SAS file and enables access to a password-protected SAS file

ENCRYPT= Data Set Option

Encrypts SAS data files

PW= Data Set Option Assigns a read, write, or alter password to a SAS file and enables access to a password-protected SAS file

READ= Data Set Option Assigns a read password to a SAS file and enables access to a read-protected SAS file

WRITE= Data Set Option Assigns a write password to a SAS file and enables access to a write-protected SAS file

Examples: Securitydata work.secure1 (alter=NoErrors);

set work.sales;run;

data work.secure2;set work.sales (alter=NoErrors);run;

* Note: A SAS password does not control access to a SAS file beyond the SAS system. You should use the operating system-supplied utilities and file-system security controls in order to control access to SAS files outside of SAS.;

data work.secure3 (encrypt=yes pw=Scramble);set work.sales;run;

proc sort data=work.secure3 (pw=scramble) out=work.secure4;by state sales;run;



SAS Data Set Option

Description

Data Set Attributes

COMPRESS= Data Set Option

Controls the compression of observations in an output SAS data set

GENMAX= Data Set Option

Requests generations for a data set and specifies the maximum number of versions

INDEX= Data Set Option

Defines indexes when a SAS data set is created

LABEL= Data Set Option

Specifies a label for the SAS data set

Examples: Data Set Attributes

data work.compress1 (compress=yes label="Attempt at Compression");set work.sales;run;

data work.masterSalesDataset (genmax=3);set work.sales;run;

data work.masterSalesDataset;set work.masterSalesDataset work.selectObs1;run;

data work.masterSalesDataset;set work.sales work.selectObs1;run;

Outline




Input and Output Datasets

• If a data set option is associated with an input data set, the action applies to the data set that is being read.

• If the option appears in the DATA statement or after an output data set specification in a PROC step, SAS applies the action to the output data set.


Input and Output Datasets

data _null_;run;

data;run;

data _null_;set _null_;if _n_ ge 0 then put 'hello';run;

data _null_;if _n_ ge 0 then put 'hello';set _null_;run;

Order of Execution

• When data set options appear on both input and output data sets in the same DATA or PROC step, SAS applies data set options to input data sets before it evaluates programming statements or before it applies data set options to output data sets.

• Likewise, data set options that are specified for the data set being created are applied after programming statements are processed.


Order of Execution

data work.salesReformat4 (rename=(sales=monthlySales));set work.sales;sales = sales/12;run;

data work.salesReformat5;set work.sales (rename=(sales=monthlySales));monthlySales = monthlySales/12;run;

Specification Conflicts

• In some instances, data set options conflict when they are used in the same statement. For example, you cannot specify both the DROP= and KEEP= options for the same variable in the same statement.


Statement Definition

• A SAS statement is a series of items that may include keywords, SAS names, special characters, and operators.

• All SAS statements end with a semicolon.

• A SAS statement either requests SAS to perform an operation or gives information to the system.


Timing Conflicts

• Timing can also be an issue in some cases. For example, if using KEEP= and RENAME= on a data set specified in the SET statement, KEEP= needs to use the original variable names, because SAS will process KEEP= before the data set is read. The new names specified in RENAME= will apply to the programming statements that follow the SET statement.


Timing Conflicts

proc sort data=work.sales (keep=sales state rename=(sales=monthlySales))

out=work.salesReformat6;by state monthlySales;run;

proc sort data=work.sales (rename=(sales=monthlySales) keep=sales state)

out=work.salesReformat7;by state monthlySales;run;

Overriding System Options

• Many system options and data set options share the same name and have the same function.

• The data set option overrides the system option for the data set in the step in which it appears.

• System options remain in effect for all DATA and PROC steps in a SAS job or session, unless they are respecified.


Conclusion

• DATA set options allow features during data step processing

• The SAS System Documentation provides specific details on the syntax

Contact Information

• Mark TabladilloMarkTab Consultinghttp://www.marktab.com/

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