Why does the SAS INFILE statement truncate one letter of a character column?

The SAS INFILE statement can sometimes truncate one letter of a character column due to a mismatch between the length specified in the INPUT statement and the actual length of the data in the input file. Here's a breakdown of why this happens and how to address it:

1. Fixed-Width Input:

- When using fixed-width input (e.g., `INPUT variable $10.`), SAS expects each value to occupy exactly the specified number of positions. If a value is shorter than the specified length, SAS will pad it with blanks. However, if a value is longer, SAS will truncate it to fit the defined length.

2. Example of Truncation:

- Suppose you have a data file where a column named `Name` has values like "John", "Alice", and "Christopher". If your SAS code uses `INPUT Name $5.`, SAS will read "John " (with a trailing space) correctly, but it will truncate "Christopher" to "Chris".

3. Delimiter Issues:

- If you are using delimited input (e.g., comma-separated or tab-separated), and the delimiter is not correctly specified or if there are inconsistencies in the delimiters, SAS might misinterpret the data and truncate values.

4. Incorrect Length Specification:

- If the length specified in the INPUT statement is shorter than the actual length of the data in the file, SAS will truncate the data to fit the specified length. For example, `INPUT Name $8.` will truncate any name longer than 8 characters.

5. Solutions:

- Use a Larger Length: If you know the maximum length of the character data, specify a length in the INPUT statement that is equal to or greater than the maximum length. For example, `INPUT Name $20.`

- Use List Input: If the data is delimited, use list input (e.g., `INPUT Name $;`) which reads data until it encounters a delimiter. This is more flexible for variable-length data.

- Use Formatted Input: If you have a specific format for your data, use formatted input with the appropriate format specifiers (e.g., `INPUT Name :$CHAR20.;`).

- Check Delimiters: Ensure that the delimiter specified in the INFILE statement matches the delimiter used in the data file. For example, `INFILE 'your_file.txt' DELIMITER=',';` for comma-separated files.

6. Example of Corrected Code:

DATA mydata;
  INFILE 'your_file.txt' DELIMITER=',' MISSOVER;
  INPUT Name $20.;
RUN;

By carefully specifying the length of character variables in the INPUT statement and ensuring that the delimiters are correctly defined, you can prevent SAS from truncating data during the import process. Always verify the structure of your input file and adjust your SAS code accordingly.

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