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

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.

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 )

Outline Define data set options Provide examples in four categories Discuss data set processing rules

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 Dataset data 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', ,500000)); output work.sales; end; run;

List of Common Options SAS Data Set OptionDescription 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;

List of Common Options SAS Data Set OptionDescription Observation Control FIRSTOBS= Data Set Option Specifies which observation SAS processes first IN= Data Set OptionCreates a variable that indicates whether the data set contributed data to the current observation OBS= Data Set OptionSpecifies 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;

List of Common Options SAS Data Set OptionDescription SecurityALTER= 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: Security data 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;

List of Common Options SAS Data Set OptionDescription 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 Define data set options Provide examples in four categories Discuss data set processing rules

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 Tabladillo MarkTab Consulting