represents data that is missing.
specifies a reason for the data's being missing.
associates the expression expr with the missing data.
- 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.
Wolfram Research (2007), Missing, Wolfram Language function, https://reference.wolfram.com/language/ref/Missing.html (updated 2014).
Wolfram Language. 2007. "Missing." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/Missing.html.
Wolfram Language. (2007). Missing. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Missing.html