.. _responses-response_functions-field_responses:

"""""""""""""""
field_responses
"""""""""""""""


Number of field responses functions


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

   responses-response_functions-field_responses-lengths
   responses-response_functions-field_responses-num_coordinates_per_field
   responses-response_functions-field_responses-read_field_coordinates


**Specification**

- *Alias:* num_field_responses 

- *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-response_functions-field_responses-lengths.html
__ responses-response_functions-field_responses-num_coordinates_per_field.html
__ responses-response_functions-field_responses-read_field_coordinates.html



**Description**


This keyword describes the number of field response 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 responses and field responses 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_response``, 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 responses, the user should specify
the number of scalar responses as ``scalar_responses``.  If there are only field responses,
it still is necessary to specify both ``response_functions`` = NN and ``field_responses`` = NN,
where NN is the number of field responses.

This type of data set is used by uncertainty
quantification methods, in which the effect of parameter uncertainty
on response functions is quantified, and can also be used in parameter
study and design of experiments methods (although these methods are
not restricted to this data set), in which the effect of parameter
variations on response functions is evaluated.
Currently, field response functions will be translated back to scalar responses.
So, a field of length 100 will be treated as 100 separate scalar responses.
However, in future versions of Dakota, we plan to implement methods which can exploit the nature of field data.


