Data Preparation in SAS

Preparing Data in SAS

• Reading and Filtering Data:

  • Create a copy of data using DATA output-table; RUN; SET input-table;
  • Filter rows using DATA output-table; RUN; SET input-table; WHERE expression;
  • Specify columns for the output dataset with DROP or KEEP in the DATA step.

• Specifying Columns:

  • Include or exclude columns using DROP and KEEP statements.
  • Example: DROP col-name <col-name>; or KEEP col-name <col-name>;

• Formatting Columns:

  • Format columns within the DATA step using FORMAT statement.
  • Example: FORMAT col-name format;

• Computing New Columns:

  • Create new columns using expressions.
  • Example: new-column = expression; in the DATA step.
  • The column name to create or update is on the left. The expression for computation is on the right.
  • New numeric columns are 8 characters long.
  • Character columns automatically adjust length to the value assigned length. Character strings must be quoted and are case sensitive.

• Example using functions: -Example : LENGTH char-column $ length; -Calculates summary stats (ignoring missing values): function(argument1, argument2, ...)

• Functions:

  • Calculates common functions like sum, mean, median, range, min, max, count (non-missing and missing).
  • Character functions include changing case (upper/lower/proper) and concatenation.
  • Date functions extract values (month, year, day, weekday, quarter) or create SAS dates.

Conditional Processing

• IF-THEN:

  • Execute a statement if a condition is met.
  • IF expression THEN statement;

• IF-THEN-ELSE:

  • Execute one statement if a condition is true and another if it's false.
  • IF expression THEN statement; ELSE statement;

• IF-THEN-DO:

  • Execute multiple statements if a condition is true.
  • IF expression THEN DO; <statements>; END;

• Example of using IF-THEN-ELSE and IF-THEN-DO.