.. auto-generated by dev_tools.docs.nxdl from the NXDL source base_classes/NXfit_function.nxdl.xml -- DO NOT EDIT

.. index::
    ! NXfit_function (base class)
    ! fit_function (base class)
    see: fit_function (base class); NXfit_function

.. _NXfit_function:

==============
NXfit_function
==============

**Status**:

  base class, extends :ref:`NXobject`

**Description**:

  .. collapse:: This describes a fit function that is used to fit data to any functional form. ...

      This describes a fit function that is used to fit data to any functional form.

      A fit function is used to describe a set of data :math:`y_k, k = 1 ... M`,  which are collected as a function
      of one or more independent variables :math:`x` at the points :math:`x_k`. The fit function :math:`f` describes
      these data in an approximate way as :math:`y_k \approx f(a_0, . . . a_n, x_k)`,
      where :math:`a_i, i = 0 . . . n` are the *fit parameters* (which are stored the instances of ``NXfit_parameter``).

**Symbols**:

  No symbol table

**Groups cited**:
  :ref:`NXparameters`

.. index:: NXparameters (base class); used in base class

**Structure**:

  .. _/NXfit_function/function_type-field:

  .. index:: function_type (field)

  **function_type**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Type of function used. ...

        Type of function used.

        Examples include "Gaussian" and "Lorentzian". In case a complicated functions, the the functional
        form of the function should be given by the ``formula_description`` field . The user is also encouraged
        to use the ``description`` field for describing the fit function in a human-readable way.

        Application definitions may limit the allowed fit functions by using an enumeration for the ``function_type`` field.

  .. _/NXfit_function/description-field:

  .. index:: description (field)

  **description**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Human-readable short description of this fit function. ...

        Human-readable short description of this fit function.
        Software tools may use this field to write their local description of the fit function.

  .. _/NXfit_function/formula_description-field:

  .. index:: formula_description (field)

  **formula_description**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Description of the mathematical formula of the function, taking into account t ...

        Description of the mathematical formula of the function, taking into account the
        instances of ``TERM`` in ``fit_parameters``.

  .. _/NXfit_function/fit_parameters-group:

  **fit_parameters**: (optional) :ref:`NXparameters` :ref:`⤆ </NXobject/PARAMETERS-group>`


    .. _/NXfit_function/fit_parameters/PARAMETER-field:

    .. index:: PARAMETER (field)

    :bolditalic:`PARAMETER`: (optional) :ref:`NX_CHAR_OR_NUMBER <NX_CHAR_OR_NUMBER>` {units=\ :ref:`NX_ANY <NX_ANY>`} :ref:`⤆ </NXparameters/PARAMETER-field>`

      .. collapse:: A parameter for a fit function. ...

          A parameter for a fit function.
          This would typically be a variable that
          is optimized in a fit.

      .. _/NXfit_function/fit_parameters/PARAMETER@description-attribute:

      .. index:: description (field attribute)

      **@description**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

        A description of what this parameter represents.

      .. _/NXfit_function/fit_parameters/PARAMETER@fixed-attribute:

      .. index:: fixed (field attribute)

      **@fixed**: (optional) :ref:`NX_BOOLEAN <NX_BOOLEAN>` 

        If the parameter is held constant, then this attribute should be True.

      .. _/NXfit_function/fit_parameters/PARAMETER@min_value-attribute:

      .. index:: min_value (field attribute)

      **@min_value**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` 

        The minimal value of the parameter, to be used as a constraint during fitting.

      .. _/NXfit_function/fit_parameters/PARAMETER@max_value-attribute:

      .. index:: max_value (field attribute)

      **@max_value**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` 

        The maximal value of the parameter, to be used as a constraint during fitting.


Hypertext Anchors
-----------------

List of hypertext anchors for all groups, fields,
attributes, and links defined in this class.


* :ref:`/NXfit_function/description-field </NXfit_function/description-field>`
* :ref:`/NXfit_function/fit_parameters-group </NXfit_function/fit_parameters-group>`
* :ref:`/NXfit_function/fit_parameters/PARAMETER-field </NXfit_function/fit_parameters/PARAMETER-field>`
* :ref:`/NXfit_function/fit_parameters/PARAMETER@description-attribute </NXfit_function/fit_parameters/PARAMETER@description-attribute>`
* :ref:`/NXfit_function/fit_parameters/PARAMETER@fixed-attribute </NXfit_function/fit_parameters/PARAMETER@fixed-attribute>`
* :ref:`/NXfit_function/fit_parameters/PARAMETER@max_value-attribute </NXfit_function/fit_parameters/PARAMETER@max_value-attribute>`
* :ref:`/NXfit_function/fit_parameters/PARAMETER@min_value-attribute </NXfit_function/fit_parameters/PARAMETER@min_value-attribute>`
* :ref:`/NXfit_function/formula_description-field </NXfit_function/formula_description-field>`
* :ref:`/NXfit_function/function_type-field </NXfit_function/function_type-field>`

**NXDL Source**:
  https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/base_classes/NXfit_function.nxdl.xml