introduction to sas data set options

Introduction to Data Set Options

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

January 30, 2007

IntroductionIntroduction

• Data set options allow features duringData set options allow features during dataset processing

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

• Data set options allow the data step to t l i bl b ti itcontrol variables, observations, security,

and data set attributes

OutlineOutline

• Define data set optionsDefine data set options• Provide examples in four categories

Di d t t i l• Discuss data set processing rules

DefinitionDefinition

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

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

SyntaxSyntax

• Specify a data set option in parenthesesSpecify a data set option in parentheses after a SAS data set name. To specify several data set options separate themseveral data set options, separate them with spaces. (option 1=value 1< option n=value n>)(option-1=value-1<...option-n=value-n>)


OutlineOutline



Quick ExamplesQuick Examples

• Data set options enable us to performData set options enable us to perform operations such as these:

Renaming variables– Renaming variables– Selecting only the first or last n observations

for processingfor processing– Dropping variables from processing or from

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


Common Option CategoriesCommon Option Categories

• Variable ControlVariable Control• Observation Control

S it• Security• Data Set Attributes

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

length state $2 sales 8 randomState 3;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;

l t( d St t )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));sales = int(rand('gaussian',1000000,500000));output work.sales;

end;end;run;

List of Common OptionsList of Common OptionsSAS 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 p g psets

RENAME= Data Set O i

Changes the name of a variableOption

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

Examples: Variable ControlExamples: Variable Control

data work salesReformat;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;


Observation FIRSTOBS= Data Set Specifies which observation SAS Control Option 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 observationsobse a o s

WHERE= Data Set Option

Selects observations that meet the specified condition


Examples: Observation ControlExamples: 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 ControlExamples: Observation Control

data work combineObs1;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;data work.combineObs2;set work.selectObs1 (in=in1) work.selectObs2 (in=in2);if in1 and in2 then output;run;


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 aSAS 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


SAS file

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

set work.sales;run;

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


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 D S D fi i d h SAS dINDEX= Data Set Option

Defines indexes when a SAS data set is created

LABEL= Data Set Specifies a label for the SAS data setOption


Examples: Data Set AttributesExamples: Data Set Attributesdata work.compress1 (compress=yes label="Attempt at Compression");

set work.sales;run;

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

d t k t S l D t tdata work.masterSalesDataset;set work.masterSalesDataset work.selectObs1;run;

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

OutlineOutline



Input and Output DatasetsInput and Output Datasets

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

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


Input and Output DatasetsInput and Output Datasets

d t lldata _null_;run;

data;;run;

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

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

Order of ExecutionOrder of Execution

• When data set options appear on both input andWhen 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 d t tdata sets.

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


Order of ExecutionOrder of Execution

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

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

Specification ConflictsSpecification Conflicts

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


Statement DefinitionStatement Definition

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

• All SAS statements end with a semicolon. A SAS t t t ith t SAS t• A SAS statement either requests SAS to perform an operation or gives information t th tto the system.


Timing ConflictsTiming Conflicts

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


Timing ConflictsTiming Conflicts

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

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

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

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

Overriding System OptionsOverriding System Options

• Many system options and data set optionsMany 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 p pit appears.

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


ConclusionConclusion

• DATA set options allow features duringDATA set options allow features during data step processing

• The SAS System Documentation provides• The SAS System Documentation provides specific details on the syntax

Contact InformationContact Information

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

introduction to sas data set options

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