Conditional Logic in SAS – IF-ELSE and DO Statement

Welcome back to Mindful Data Minds! In this session, we’ll learn how to use IF-ELSE statements to apply conditions in SAS, and how the DO statement helps when multiple actions need to be performed under one condition.

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What You Will Learn

• How to use IF-ELSE for conditional logic.
• How to avoid truncation issues with character variables.
• How to output data into multiple datasets in one step.
• How to use DO…END for multiple actions under one condition.
• How to apply business rules (like discounts) using conditional logic.

Using IF-ELSE in SAS

The IF-ELSE statement lets you apply logic to create new variables or categorize data.

Example: Categorizing Car Speed by Horsepower

data a;
   sashelp.cars;
   if horsepower <= 250 then speed = "Slow";
   else if 250 < horsepower <= 400 then speed = "Medium";
   else speed = "Fast";
run;

Result: A new column Speed is created based on horsepower.

Note: By default, SAS sets the length of character variables based on the first value it encounters. If the first value is “Slow” (4 characters), longer values like “Medium” may get truncated

Solution: Define a format or length:

format speed $10.;

Creating Multiple Datasets with IF-ELSE

You can output data into different datasets in a single step:

data slow medium fast;
   set b;
   if strip(lowcase(speed)) = "slow" then output slow;
   else if strip(lowcase(speed)) = "medium" then output medium;
   else output fast;
run;

Result: Three datasets (slow, medium, fast) created based on speed categories.

Using DO Statement

When multiple actions are needed under one condition, use DO…END.

Example: Applying Discounts Based on Speed

data c;
   set b;
   if strip(lowcase(speed)) = "slow" then do;
      discount = 10;
      updated_msrp = msrp - (msrp * discount / 100);
   end;
   else if strip(lowcase(speed)) = "medium" then do;
      discount = 5;
      updated_msrp = msrp - (msrp * discount / 100);
   end;
   else do;
      discount = 0;
      updated_msrp = msrp;
   end;
run;

Result:

• Slow cars → 10% discount
• Medium cars → 5% discount
• Fast cars → No discount

The dataset now includes Discount and Updated MSRP columns.

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