.. _responses-objective_functions-field_objectives:

""""""""""""""""
field_objectives
""""""""""""""""


Number of field objective functions


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

   responses-objective_functions-field_objectives-lengths
   responses-objective_functions-field_objectives-num_coordinates_per_field
   responses-objective_functions-field_objectives-read_field_coordinates


**Specification**

- *Alias:* num_field_objectives 

- *Arguments:* INTEGER


**Child Keywords:**

+-------------------------+--------------------+-------------------------------+-----------------------------------------------+
| Required/Optional       | Description of     | Dakota Keyword                | Dakota Keyword Description                    |
|                         | Group              |                               |                                               |
+=========================+====================+===============================+===============================================+
| Required                                     | `lengths`__                   | Lengths of field responses                    |
+----------------------------------------------+-------------------------------+-----------------------------------------------+
| Optional                                     | `num_coordinates_per_field`__ | Number of independent coordinates for field   |
|                                              |                               | responses                                     |
+----------------------------------------------+-------------------------------+-----------------------------------------------+
| Optional                                     | `read_field_coordinates`__    | Add context to data: flag to indicate that    |
|                                              |                               | field coordinates should be read              |
+----------------------------------------------+-------------------------------+-----------------------------------------------+

.. __: responses-objective_functions-field_objectives-lengths.html
__ responses-objective_functions-field_objectives-num_coordinates_per_field.html
__ responses-objective_functions-field_objectives-read_field_coordinates.html



**Description**


This keyword describes the number of field objective functions.
A field function is a set of related response values collected over a range of
independent coordinate values which may or may not be specified by the user.
For example, voltage over time would be a field function, where voltage is
the ``field_objective`` and time is the independent coordinate.
Similarly, temperature over time and space would be a field response, where the
independent coordinates would be both time and spatial coordinates such as (x,y) or (x,y,z), depending on the application.
The main difference between scalar objectives and field objectives is that for field data, we
plan to implement methods that take advantage of the correlation or relationship between
the field values.

Note that if there is one ``field_objective``, and it has length 100 (meaning 100 values), then
the user's simulation code must return 100 values.
Also, if there are both scalar and field objectives, the user should specify
the number of scalar objectives as ``scalar_objectives``.  If there are only field objectives,
it still is necessary to specify both ``objective_functions`` = NN and ``field_objectives`` = NN,
where NN is the number of field objectives.

Objective functions are responses that are used with optimization
methods in Dakota.  Currently, each term in a field objective is added
to the total objective function presented to the optimizer.  For example,
if you have one field objective with 100 terms (e.g. a time-temperature trace
with 100 time points and 100 corresponding temperature points), the 100 temperature values
will be added to create the overall objective.


