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Convert Character To Numeric In SAS: A Complete Guide

9 min read 11-15- 2024
Convert Character To Numeric In SAS: A Complete Guide

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Converting character data to numeric data in SAS can often be a necessity, especially when dealing with datasets that require mathematical operations. In this guide, we will delve into the methods for converting character values to numeric values in SAS, ensuring you grasp the concepts and techniques to effectively manage your data. We'll explore various functions, practical examples, and potential pitfalls you might encounter along the way.

Understanding Character and Numeric Data in SAS

Before we get into the specifics of converting data types, let's clarify what character and numeric data types are in SAS.

  • Character Data: This type of data is made up of letters, numbers, and symbols. It is usually contained in quotes and is used to represent non-numeric information such as names, addresses, and categorical values.

  • Numeric Data: Numeric data consists solely of numbers, which can be used in calculations, mathematical operations, and statistical analyses.

Why Convert Character to Numeric?

There are several reasons why you might need to convert character data to numeric:

  1. Data Analysis: Many statistical analyses require numeric input. If your dataset contains numbers stored as characters, you won't be able to perform calculations directly.

  2. Sorting and Comparisons: Numeric data can be sorted and compared more efficiently than character data.

  3. Creating Derived Variables: You may need to create new variables that are based on calculations involving existing numeric values.

Common Functions for Conversion

SAS provides a variety of functions that can be used to convert character data to numeric data. Below are some of the most common functions:

  • INPUT Function: The most widely used function for converting character to numeric.

  • BEST. format: Often used with the INPUT function to specify the type of numeric conversion.

Using the INPUT Function

The INPUT function is your go-to method for converting character values to numeric in SAS. Here’s the basic syntax:

NEW_NUM_VAR = INPUT(CHAR_VAR, NUM_FORMAT.);
  • NEW_NUM_VAR: The new numeric variable you are creating.
  • CHAR_VAR: The character variable you are converting.
  • NUM_FORMAT: The format of the numeric variable you are converting to (e.g., BEST.).

Example 1: Basic Conversion

Let’s say you have a dataset containing a character variable representing age.

data ages;
    input age_char $;
    age_num = INPUT(age_char, BEST.);
    datalines;
25
30
45
;
run;

proc print data=ages;
run;

Key Points:

  • In this example, the age_char variable is converted to a new variable age_num using the INPUT function and the BEST. format.

Example 2: Handling Non-Numeric Values

Not all character variables will convert cleanly. If a character variable contains non-numeric values, the conversion will result in a missing value for that observation.

data mixed_ages;
    input age_char $;
    age_num = INPUT(age_char, BEST.);
    datalines;
25
invalid
30
;
run;

proc print data=mixed_ages;
run;

In this example, the second record will yield a missing value for age_num because invalid cannot be converted to a number.

Important Notes

Always Check for Validity: After conversion, it's essential to check for any missing values that might result from invalid character data.

Using Formats to Control Input and Output

The INPUT function's second argument can take various numeric formats. For instance:

  • BEST.: General numeric format.
  • COMMA.: Numeric format with commas.
  • DOLLAR.: Numeric format with dollar signs.

This can help manage how you interpret the character data and how you want it represented numerically.

Example 3: Using COMMA Format

If your character data includes comma-separated values:

data sales;
    input sales_char $;
    sales_num = INPUT(sales_char, COMMA.);
    datalines;
1,000
2,500
;
run;

proc print data=sales;
run;

Converting Dates from Character to Numeric

When dealing with dates in character format, the conversion requires special attention. You can use the INPUT function along with appropriate date formats.

Example 4: Date Conversion

data dates;
    input date_char $10.;
    date_num = INPUT(date_char, DATE9.);
    format date_num DATE9.;
    datalines;
01JAN2020
15FEB2021
;
run;

proc print data=dates;
run;

Key Points:

  • In the example above, the DATE9. format is used to convert character dates to numeric date values.

Handling Leading and Trailing Spaces

Spaces in character strings can affect conversions. The STRIP function can be employed to remove leading and trailing spaces before conversion.

Example 5: Stripping Spaces

data trimmed;
    input age_char $;
    age_num = INPUT(STRIP(age_char), BEST.);
    datalines;
   25 
30
;
run;

proc print data=trimmed;
run;

Summary of Conversion Methods

Here’s a quick reference table summarizing the key methods discussed:

<table> <tr> <th>Function</th> <th>Description</th> <th>Example Format</th> </tr> <tr> <td>INPUT</td> <td>Convert character to numeric</td> <td>INPUT(var, BEST.)</td> </tr> <tr> <td>STRIP</td> <td>Remove spaces</td> <td>STRIP(var)</td> </tr> <tr> <td>DATE9.</td> <td>Format for date conversion</td> <td>INPUT(date_char, DATE9.)</td> </tr> </table>

Common Pitfalls

  1. Missing Values: Always check for missing values after conversion to handle any non-numeric cases.

  2. Format Misuse: Using the wrong format in the INPUT function can lead to errors or unintended conversions.

  3. Date Handling: Dates require specific formats for conversion, and mistakes in format can lead to errors.

  4. Non-standard Characters: Be wary of special characters in your character strings that may not convert well.

Conclusion

Converting character data to numeric in SAS is a fundamental skill that enhances your ability to analyze and manage datasets effectively. By employing the INPUT function along with various formats and functions like STRIP, you can ensure a smooth conversion process. Always keep in mind the potential pitfalls to avoid common errors, and you'll be well on your way to becoming proficient in data manipulation within SAS.

By understanding these concepts and using the examples provided, you can confidently tackle character to numeric conversions in your SAS projects. Happy coding!

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