Missing value
A cell where a value should exist and does not. The reason matters: not collected, not applicable, and lost are different situations.
Where it comes up
- Disguised missing valuesA cell is not empty, but what it holds means there is no value: N/A, a dash, 999, or the word none.
See also
- NullThe explicit marker a database or file uses for no value. It is different from zero, from an empty string, and from the text NULL typed into a cell.
- Sentinel valueAn ordinary-looking value used as a code for something else, most often 999, -1, or 1900-01-01 standing in for unknown.
- ImputationFilling in a missing value with an estimate, such as the column average or a value predicted from other columns.