Missing

Missing[]

represents data that is missing.

Missing["reason"]

specifies a reason for the data's being missing.

Missing["reason",expr]

associates the expression expr with the missing data.

Details

  • Missing[] is a symbolic object, with no default evaluation rules defined.
  • Typical examples of "reason" include "NotApplicable", "Unknown", "NotAvailable", "Nonexistent", "Indeterminate", "Variable", "Disputed", or "TooLarge".
  • Missing can be returned by most data functions, such as CountryData and ElementData.
  • Missing is returned when a key requested in an Association is not found.
  • Plotting functions automatically omit Missing objects when plotting data.
  • In TraditionalForm, Missing is typically formatted as , with a tooltip specifying the reason.

Examples

Basic Examples  (4)

When properties are missing, a Missing object is returned:

Missing is generated when an association does not contain the specified key:

Missing elements can be filtered out using DeleteCases:

Visualization typically automatically filters out Missing elements:

Introduced in 2007
 (6.0)
 |
Updated in 2014
 (10.0)