This page summarizes the SAS material required for this class. It also indicates the material required for the SAS Quiz (i.e. Quiz #3 - except for Summer Sessions).

Readings:

The following chapters refer to the text "SAS Manual for Moore and McCabe's Introduction to the Practice of Statistics, Evans." You may want to review these chapters if you have the text.

• Chapter 1: pp13 - 24; pp37 - 40
• Chapter 2: pp50 - 53
• Chapter 2: pp56 - 58; pp75 - 76; pp78 - 81; pp83 - 87 (not required for SAS Quiz)

The following chapters refer to the text "SAS System for Elementary Statistical Analysis, Schlotzhauer & Littell." You may want to review these chapters if you have the text.
Note: SAS Handouts #2 and #3 are from these chapters.

• Chapter 2: pp27 - 30
• Chapter 3: pp41 - 53
• Chapter 4: pp80 - 86 (PROC UNIVARIATE) (not required for SAS Quiz)
• Chapter 4: pp86 - 87 (PROC MEANS)
• Chapter 9: pp286 - 289 (not required for SAS Quiz)

The textbook readings above may not cover all the material required. The material below is a summary of the textbook readings plus additional required topics. Remember to pay particular attention to the rules summarized in the Basic Rules section below.

Note: For the SAS Quiz, you should expect three questions. The topics for each question are:

• General statements and DATA step statements
• PROC step statements
• A SAS program with syntax errors. You will be expected to find and fix the errors.

Review:

• Basic Rules:
  • All SAS programs consist of a sequence of statements organized into "steps". There are only two kinds of steps:
    • DATA step:
    • PROC step:
      Note:Once a dataset has been created, it can be processed by any subsequent "DATA" or "PROC" step.
  • A SAS program can contain any number of "DATA" and "PROC" steps.
  • All SAS statements start with a keyword (DATA, INPUT, PROC, etc.).
  • All SAS statements end with a semicolon ";".
  • SAS statements can be entered in free-format. That is, they can begin in any column; there may be multiple statements per line; you may split a statement over several lines (as long as no word is split.).
  • Uppercase and lowercase are equivalent, except inside quote marks (lang = 'c'; is not the same as lang = 'C';).
  • Naming Convention:
  1. 32 characters in length (Note: v6.12 users: 8 characters in length)
  2. begin with A-Z or _(i.e. underscore)
  3. cannot contain blanks or special symbols (e.g., &, %, $, #, etc.)
  • SAS Types:
  1. Character variables (followed by $)
  2. Numeric variables
  Note:Missing data: represented by '.' for numeric variables; by ' ' (i.e. space) for character variables.

• General statements:

These are statements that do not belong to a particular DATA or PROC step. They have a global effect.

• footnote statement
• title statement
• options statement

• DATA step statements:

SAS carries out all statements in the DATA step in order for each input observation .

1. The "DATA" statement identifies the start of a DATA step and names the data structure to be created.

	DATA <dataset_name>;
    

2. The "INFILE" statement identifies an external file from which data will be read (see Guide 5 for an example).

	INFILE <file_name>;
    

3. The "DATALINES" statement is used if you choose to embed data in your program instead of reading it from an external file.

	DATALINES;
    

4. The "INPUT" statement defines variables, their type, and specifies how data is to be read:

	 INPUT <variable_name [type] [position]>...;

         Example:
	 i)   INPUT MFG @@; 
	 ii)  INPUT MFG $ TYPE $ SEEK TRANSFER;
	 iii) INPUT MFG $ 1-8 TYPE $ 11-12 SEEK 13-16 TRANSFER 17-19;
    

5. Variables may be given descriptive names (see Guide 3 for an example):

   	 LABEL <variable_name='label'>...;
   
            Example:
   	 i)  LABEL MFG='Manufacturer'; 
   	 ii) LABEL MFG='Manufacturer'  
   	   	      SEEK='Seek Time'; 
   

6. Assignment statements create new variables (see Guide 6 for an example). The usual arithmetic operators are available:

	Symbol Operation             Example

	**     Exponentiation        Z=X**2;
	*      Multiplication        Z=X*Y;
	/      Division              Z=X/Y;
	+      Addition              Z=X+Y;
	-      Subtraction           Z=X-Y;
    

Note: Parentheses may be used to override the operator precedence hierarchy. So, any part of an expression within parentheses will be evaluated first. Remember that the exponenentiation operator is at the highest level of the hierarchy, then multiplications and divisions, and then additions and subtractions.
7. The "DROP" and "KEEP" statements are used to remove variables and all associated values from a dataset (not required for SAS Quiz) :

	DROP <variable_name>...;

removes named variables from the dataset and keeps unnamed variables.

	KEEP <variable_name>...;

keeps named variables and drops unnamed variables from the dataset.
8. The "IF" statement is used for conditional processing. Note that expression is a boolean expression that evaluates to T or F and so statement T is executed if it evaluates to T and statement F if it evaluates to F.
   (not required for SAS Quiz) :

	IF <expression> THEN <statement T>;
	ELSE <statement F>;

Note: The ELSE statement is optional but, if present, must immediately follow the associated IF statement. The IF ... THEN part comprises a single statement:

	i)  IF SEEK < 15 THEN CLASS = 'FAST';
	    ELSE CLASS = 'SLOW';
	ii) CLASS='SLOW';
	    IF SEEK < 15 THEN CLASS = 'FAST';

SAS comparison operators are shown below. You can use either the symbol or the two-letter abbreviation.

	Symbol     Abbrev

	<, <=      LT, LE  
	>, >=      GT, GE  
	=, ^=      EQ, NE  

SAS also provides logical operators for more complex boolean expressions. Either the symbol or word may be used.

	Symbol  Connective

	 &        AND  
	 |        OR  
 	 ^        NOT  

A special form of the "IF" statement is used for subsetting a dataset, that is selecting/excluding particular observations.

	DATA CDROM;
	INPUT MFG $ TYPE $ SEEK TRANSFER;
	IF SEEK < 15;

The statement IF SEEK < 15; is equivalent to:

i)  IF SEEK < 15 THEN OUTPUT;
ii) IF SEEK >=15 THEN DELETE;
    

The example below excludes those observations where seek is 15 or more:

	DATA CDROM;
	INPUT MFG $ TYPE $ SEEK TRANSFER;
	IF SEEK < 15;
	DATALINES;
	NEC 12X 7.3 105
	SONY 6X 23.1 830
	SONY 4X 40.1 330
	CANON 6X 13.5 530
	SONY 12X 5.5 1000

The dataset CDROM will therefore contain observations 1, 4 and 5 only:


	NEC 12X 7.3 105
	CANON 6X 13.5 530
	SONY 12X 5.5 1000

9. Comments:

Two types of comments:

	i)	* ... ;
	ii)	/* ... */
	
	DATA CDROM;
	* Read in variables;
	INPUT MFG $ TYPE $ TRANSFER SEEK;
	/*  ignore next statement
	SEEKMIN = SEEK/60000;
	*/
  



• PROC step statements:

SAS procedures execute predefined procedures which may be either statistical or utility procedures. The data structure processed is the most recently created dataset unless otherwise specified in a "DATA=" option.

	PROC <procedure_name>;
	[procedure_statement];
    


"procedure_statement" typically depends on the procedure but some may be used with all procedures:

	 VAR <variable_name>;


Indicates which variables are to be analyzed. If this statement is omitted, the default is to include all variables of the appropriate type.



	 BY <variable_name>;


Used primarily with the SORT procedure in which case it cannot be omitted.



You should be familiar with the following procedures:

1. Correlations among a set of variables: (not required for SAS Quiz)

	PROC CORR [options];
	  [VAR <variable_name>;]
    

2. Means, standard deviations, and other univariate statistics (N; MEAN; STD; MIN; MAX; SUM; VAR):

	PROC MEANS [options];
	  [VAR <variable_name>...;]
    

3. Univariate statistics. That is means, standard deviations, median etc. Also provides options to generate a p-value for a normality test and to produce the box plot, stem & leaf and normal plots: (not required for SAS Quiz)

	PROC UNIVARIATE [options];
	  [VAR <variable_name>...;]
    

4. Print a SAS data set:

	PROC PRINT [options];
	  [VAR <variable_name>...;]
    

5. Sort a SAS data set according to one or more variables:

	PROC SORT [options];
	  BY <variable_name>...;
  

6. Plot y against x. May be used to create a scatter plot or a residual plot (not required for SAS Quiz):

	PROC PLOT [options];
 	  PLOT <dep_var_name>*<indep_var_name>='*' [options];

  

7. Produce coefficients of the simple linear regression equation. (not required for SAS Quiz):

	PROC REG [options];
 	  MODEL <dep_var_name>=<indep_var_name>;

  

If residuals are needed then the optional output statement must be included. The dataset specified in the out= option will be created and will include the contents of the original dataset processed in addition to the variable specified in the r= option which will include the residuals.

	PROC REG [options];
 	  MODEL <dep_var_name>=<indep_var_name>;
 	  OUPUT OUT=<dataset> r=<var_name>;
  

See guide 5 (output) for an example. Also, see the income/gpa sample program.