# Treating data values as missing

Many data sets use special values (such as 999) to indicate missing values. To exclude such missing values from Wizard’s calculations:

1. In the Summary view, select the column or columns for which you wish to define missing values
2. Choose Column > Define Missing Values…
3. Use the predicate editor to define conditions for missingness, and press OK when you are finished

Empty data values are always treated as missing.

See also:

- Copying another column’s missing values
- Treating a column as categorical data
- About recode variables

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