How To Convert Character To Numeric In Sas

How to Convert Character to Numeric in SAS: A Comprehensive Guide

Converting character variables to numeric variables in SAS is a common task, especially when working with data imported from external sources or when needing to perform numerical calculations on variables initially stored as text. This comprehensive guide will walk you through various methods, addressing common pitfalls and providing best practices for a smooth and efficient conversion process. Understanding these techniques is crucial for data cleaning, analysis, and reporting in SAS.

Understanding the Challenge: Character vs. Numeric Variables

Before diving into the conversion methods, it's essential to grasp the fundamental difference between character and numeric variables in SAS.

• Character variables: Store textual data, including numbers represented as text strings. They can contain letters, numbers, special characters, and spaces. They are identified by a $ symbol in the variable name or in the data set definition.

• Numeric variables: Store numerical data suitable for mathematical operations. They cannot contain letters, spaces, or special characters (except a decimal point for floating-point numbers).

The primary challenge in converting character to numeric lies in handling potential non-numeric characters within the character variable. If a character variable contains even a single non-numeric character, a direct conversion will likely fail, resulting in errors or unexpected results.

Methods for Character to Numeric Conversion in SAS

SAS offers several approaches to convert character variables to numeric variables. The best method depends on the nature of your data and the level of error handling required.

1. Using the INPUT Function

The INPUT function is a powerful and flexible tool for this conversion. It reads a character string and attempts to interpret it as a number. If the string contains non-numeric characters, the function will either return a missing value (.) or an error, depending on how you configure it.

Syntax:

new_numeric_variable = input(character_variable, informat.);

• character_variable: The name of the character variable you want to convert.
• informat.: Specifies the numeric input format. Common informats include:
  • best.: Automatically determines the best informat based on the data.
  • 8.: Reads an 8-byte integer.
  • 12.: Reads a 12-byte integer.
  • best12.: Reads up to 12 bytes, best for both integers and decimals.
  • comma12.: Reads a number with commas as thousands separators (e.g., "1,234,567").
  • dollar12.: Reads a number with a dollar sign prefix (e.g., "$1234.56").

Example:

data converted_data;
  set original_data;
  numeric_sales = input(sales_char, best.);
run;

This code converts the character variable sales_char to a numeric variable numeric_sales using the best. informat. If sales_char contains non-numeric characters, the corresponding numeric_sales value will be missing.

Handling Errors: You can improve error handling by using the informat within a DATA step:

data converted_data;
  set original_data;
  input_status = inputc(sales_char, best12.); /* inputc returns an error status */
  if input_status = 0 then do;
    numeric_sales = input(sales_char, best12.);
  end;
  else do;
    numeric_sales = .; /* handle non-numeric entries */
    put sales_char=; /* option to log problematic values for analysis*/
  end;
run;

proc print data=converted_data;
run;

2. Using the SCAN Function with the INPUT Function

If your character variable contains numbers interspersed with non-numeric characters, you can use the SCAN function to extract the numeric portion before applying the INPUT function.

Example:

Let's say you have a character variable product_code like "ABC123XYZ". To extract the numeric part "123":

data extracted_data;
  set original_data;
  numeric_code = input(scan(product_code, 2, 'A'), best.); /* Extracts the second word (123) assuming it is numeric */
run;

This code first uses SCAN(product_code, 2, 'A') to extract the second word (assuming numeric part is always the second word separated by non-numeric characters) and then converts it to numeric using INPUT.

3. Using the COMPRESS Function

The COMPRESS function removes specified characters from a string. This is particularly useful if you have consistent non-numeric characters (e.g., dollar signs, commas) that you want to remove before conversion.

Example:

To remove dollar signs and commas from a character variable price_char before conversion:

data compressed_data;
  set original_data;
  cleaned_price = compress(price_char, '