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How to Write an Array in SAS: A Comprehensive Guide for Everyday Users

2026-06-16 05:27:24

Unlocking the Power of SAS Arrays: A Step-by-Step Guide

Are you wading through mountains of data in SAS and finding yourself repeating the same operations over and over? Do you wish there was a more efficient way to manage and manipulate groups of similar variables? If so, then learning how to write an array in SAS is your next essential skill. Arrays provide a powerful way to treat a collection of variables as a single unit, streamlining your code and saving you valuable time. This guide will walk you through the process, making it accessible even if you're not a seasoned SAS programmer.

What Exactly Is a SAS Array?

Think of a SAS array as a list or a group of variables that you can refer to using a single name and an index. Instead of writing out each variable name individually, you can use the array name followed by a subscript (like a number or a name) to access one or all of the variables in the group. This is incredibly useful when you have a series of variables that represent similar data points, such as:

  • Monthly sales figures (e.g., `Sales_Jan`, `Sales_Feb`, ..., `Sales_Dec`)
  • Survey responses for a set of questions
  • Scores from different tests
  • Measurements taken at different time points

The Basic Syntax of a SAS Array

The fundamental structure for defining an array in SAS is:

ARRAY array-name {dimension} [variable-list];

Let's break this down:

  • ARRAY: This is the SAS keyword that tells the program you're about to define an array.
  • array-name: This is the name you'll give to your array. Choose a descriptive name that reflects the variables it contains (e.g., `MonthlySales`, `SurveyAnswers`).
  • {dimension}: This specifies the number of elements (variables) in your array. You can provide a specific number (e.g., `{12}`) or use special SAS keywords.
  • [variable-list]: This is where you list the actual SAS variable names that will be part of your array.

Defining an Array with Explicit Variable Names

The most straightforward way to create an array is to explicitly list all the variables you want to include. This is particularly helpful when your variables aren't sequentially named.

Example 1: An Array of Sales Figures

Let's say you have data with variables for sales in different quarters:

Q1_Sales, Q2_Sales, Q3_Sales, Q4_Sales

You can create an array like this:

data example_data;
input ID Q1_Sales Q2_Sales Q3_Sales Q4_Sales;
datalines;
1 1000 1200 1100 1300
2 1500 1400 1600 1700
;
run;

Now, let's define an array to hold these sales figures:

data example_data;
set example_data;
array QuarterlySales {4} Q1_Sales Q2_Sales Q3_Sales Q4_Sales;
/* Now you can use QuarterlySales to refer to these variables */
run;

In this example:

  • array is the keyword.
  • QuarterlySales is the name of our array.
  • {4} indicates there are 4 elements in this array.
  • Q1_Sales Q2_Sales Q3_Sales Q4_Sales are the specific variables included.

Defining an Array with Implicit Variable Names (Using SAS Keywords)

SAS offers powerful keywords to make array definition even more concise, especially when your variable names follow a pattern.

1. Using `_NUMERIC_` and `_CHARACTER_`

You can create arrays that automatically include all numeric or all character variables in your dataset. This is incredibly handy when you're adding or modifying variables and don't want to constantly update your array definition.

Example 2: Array of All Numeric Variables

Suppose your dataset has several numeric variables, and you want to sum them all up.

data example_data_numeric;
input ID Score1 Score2 Score3 Average;
datalines;
1 85 90 78 84.3
2 70 75 80 75.0
;
run;

Define an array to include all numeric variables:

data example_data_numeric;
set example_data_numeric;
array AllScores _NUMERIC_;
/* Now AllScores refers to ID, Score1, Score2, Score3, and Average */
/* You can then perform operations on these variables as a group */
run;

Example 3: Array of All Character Variables

Similarly, for character variables:

data example_data_char;
input FirstName $ LastName $ City $ State $;
datalines;
John Doe Springfield IL
Jane Smith Chicago IL
;
run;

Define an array for character variables:

data example_data_char;
set example_data_char;
array NamesAndLocations _CHARACTER_;
/* NamesAndLocations now includes FirstName, LastName, City, and State */
run;

2. Using `_ALL_`

The `_ALL_` keyword is a shortcut to include *all* variables (both numeric and character) in your array.

Example 4: Array of All Variables

Using the `example_data` from earlier, you could create an array of all variables:

data example_data;
set example_data;
array AllVariables _ALL_;
/* AllVariables would include ID, Q1_Sales, Q2_Sales, Q3_Sales, and Q4_Sales */
run;

3. Using Sequential Naming Patterns (The `$` and `#` Symbols)

This is where arrays truly shine for repetitive variable names. SAS allows you to define arrays based on variable name patterns.

  • `$` (Dollar Sign): Represents a sequence of numbers.
  • `#` (Hash Symbol): Represents a sequence of characters (less common for numerical indexing, more for character placeholders).

Example 5: Array for Sequentially Named Variables

Let's say you have sales data for 12 months named `Sales_01`, `Sales_02`, ..., `Sales_12`.

data monthly_sales;
input ID Sales_01 Sales_02 Sales_03 Sales_04 Sales_05 Sales_06 Sales_07 Sales_08 Sales_09 Sales_10 Sales_11 Sales_12;
datalines;
1 100 110 120 130 140 150 160 170 180 190 200 210
;
run;

To create an array for these:

data monthly_sales;
set monthly_sales;
array SalesMM {12} Sales_$$; /* The $$ tells SAS to look for Sales_01, Sales_02, etc. */
/* Now SalesMM[1] refers to Sales_01, SalesMM[2] to Sales_02, and so on. */
run;

Important Note: When using `$$`, SAS expects a fixed number of digits in the suffix. If you had `Sales_1`, `Sales_2`, ..., `Sales_10`, `Sales_11`, `Sales_12`, you would need to ensure consistent padding (e.g., `Sales_01`, `Sales_02`, ... `Sales_12`) for the `$$` to work correctly. If you have mixed padding, you might need to use explicit variable lists or more advanced techniques.

Accessing Array Elements

Once an array is defined, you can access its elements using the array name followed by an index in parentheses. The index can be a number or a variable that holds a number.

  • Numeric Index: `array-name{index}` (e.g., `QuarterlySales{1}`, `SalesMM{5}`)
  • Variable Index: You can use a SAS variable that contains the index number.

Example 6: Calculating Total Sales

Using the `QuarterlySales` array from Example 1, let's calculate the total sales for each observation:

data example_data;
set example_data;
array QuarterlySales {4} Q1_Sales Q2_Sales Q3_Sales Q4_Sales;
TotalSales = 0;
do i = 1 to 4;
TotalSales = TotalSales + QuarterlySales{i};
end;
run;

In this code:

  • We initialize a variable `TotalSales` to 0.
  • We use a `DO` loop to iterate from `i = 1` to `4`.
  • Inside the loop, `QuarterlySales{i}` accesses each element of the array in turn (QuarterlySales{1}, QuarterlySales{2}, etc.), and its value is added to `TotalSales`.

Using `DIM()` and `HBOUND()` / `LBOUND()`

SAS provides built-in functions to get information about your arrays, making your code more dynamic.

  • DIM(array-name): Returns the number of elements in the array.
  • HBOUND(array-name): Returns the upper bound of the array's index.
  • LBOUND(array-name): Returns the lower bound of the array's index. (Often 1, but can be customized).

Example 7: Dynamic Looping with `DIM()`

Instead of hardcoding the number of elements (like `4` in Example 6), you can use `DIM()`:

data example_data;
set example_data;
array QuarterlySales {4} Q1_Sales Q2_Sales Q3_Sales Q4_Sales;
TotalSales = 0;
do i = 1 to dim(QuarterlySales); /* Using DIM() makes it flexible */
TotalSales = TotalSales + QuarterlySales{i};
end;
run;

This is much better because if you later add `Q5_Sales` to your dataset and update the array definition, this code will still work correctly without needing to change the `4` to a `5`.

Common Use Cases for SAS Arrays

Arrays are versatile tools. Here are some common scenarios where they are invaluable:

  • Data Cleaning: Imputing missing values across a set of variables, standardizing formats.
  • Transformations: Applying the same mathematical operation to multiple variables (e.g., converting units, calculating ratios).
  • Aggregation: Summing, averaging, or finding the minimum/maximum of a group of variables.
  • Data Entry Validation: Checking if values across a set of variables meet certain criteria.
  • Reporting: Easily generating summary statistics for related variables.

A Note on Array Indexing

By default, SAS array indices start at 1. However, you can define custom starting points if needed, though this is less common for basic usage.

FAQ Section

Q1: How do I create an array if my variables don't have sequential names?

A: If your variables don't follow a pattern like `Var1`, `Var2`, etc., you can still create an array by explicitly listing them. You'll use the `ARRAY array-name {number-of-variables} variable1 variable2 variable3;` syntax, listing each variable name individually in the `variable-list` section.

Q2: Why would I use an array instead of just writing out the variable names?

A: Arrays make your code much more concise and easier to maintain. Instead of writing the same operation for 10 different variables, you write it once within a loop that iterates through the array. If you add or remove variables from the group, you often only need to update the array definition, not every line of code that uses those variables.

Q3: Can I have arrays of different types of variables (numeric and character) in the same array?

A: No, a single SAS array can only contain variables of the same type. You'll need to create separate arrays for numeric variables and character variables if you need to process both.

Q4: How do I assign a value to all elements of an array at once?

A: You can use a `DO` loop to iterate through the array and assign a value to each element. For example, to set all elements of `MyArray` to 0, you would write: do i = 1 to dim(MyArray); MyArray{i} = 0; end; You can also use a special syntax for initializing arrays upon definition, like `ARRAY MyArray{5} _temporary_ (0 0 0 0 0);` for temporary arrays or `ARRAY MyArray{5} Var1-Var5 (0);` to set all listed variables to 0.

By mastering SAS arrays, you'll be well on your way to writing more efficient, readable, and robust SAS programs. Happy coding!

How to write an array in SAS
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