.. _variables-discrete_uncertain_set-string:

""""""
string
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Discrete, epistemic uncertain variable - strings within a set



**Topics**


discrete_variables, epistemic_uncertain_variables


.. toctree::
   :hidden:
   :maxdepth: 1

   variables-discrete_uncertain_set-string-elements_per_variable
   variables-discrete_uncertain_set-string-elements
   variables-discrete_uncertain_set-string-set_probabilities
   variables-discrete_uncertain_set-string-initial_point
   variables-discrete_uncertain_set-string-descriptors


**Specification**

- *Alias:* None

- *Arguments:* INTEGER

- *Default:* no discrete uncertain set string variables


**Child Keywords:**

+-------------------------+--------------------+---------------------------+-----------------------------------------------+
| Required/Optional       | Description of     | Dakota Keyword            | Dakota Keyword Description                    |
|                         | Group              |                           |                                               |
+=========================+====================+===========================+===============================================+
| Optional                                     | `elements_per_variable`__ | Number of admissible elements for each set    |
|                                              |                           | variable                                      |
+----------------------------------------------+---------------------------+-----------------------------------------------+
| Required                                     | `elements`__              | The permissible values for each discrete      |
|                                              |                           | variable                                      |
+----------------------------------------------+---------------------------+-----------------------------------------------+
| Optional                                     | `set_probabilities`__     | This keyword defines the probabilities for    |
|                                              |                           | the various elements of discrete sets.        |
+----------------------------------------------+---------------------------+-----------------------------------------------+
| Optional                                     | `initial_point`__         | Initial values for variables                  |
+----------------------------------------------+---------------------------+-----------------------------------------------+
| Optional                                     | `descriptors`__           | Labels for the variables                      |
+----------------------------------------------+---------------------------+-----------------------------------------------+

.. __: variables-discrete_uncertain_set-string-elements_per_variable.html
__ variables-discrete_uncertain_set-string-elements.html
__ variables-discrete_uncertain_set-string-set_probabilities.html
__ variables-discrete_uncertain_set-string-initial_point.html
__ variables-discrete_uncertain_set-string-descriptors.html



**Description**


Discrete set variables may be used to specify categorical choices which are
epistemic. For example, if we have three possible forms for a physics
model (model 1, 2, or 3) and there is epistemic uncertainty about
which one is correct, a discrete uncertain set
may be used to represent this type of uncertainty.

This variable is defined by a set of strings, in which the discrete value may
take any value within the string set (for example, the set may be
defined as 'coarse', 'medium', and 'fine')

Other epistemic types include:

- :dakkw:`variables-continuous_interval_uncertain`
- :dakkw:`variables-discrete_interval_uncertain`
- discrete_uncertain_set :dakkw:`variables-discrete_uncertain_set-integer`
- discrete_uncertain_set :dakkw:`variables-discrete_uncertain_set-real`



**Examples**



.. code-block::

    discrete_uncertain_set
     string
     num_set_values 2             3
     set_values     'red' 'blue'  'coarse' 'medium' 'fine'
     descriptors    'ds1'         'ds2'




