.. auto-generated by script ../../../../utils/nxdl2rst.py from the NXDL source ../../../../base_classes/NXlog.nxdl.xml

.. index::
    ! NXlog (base class)
    ! log (base class)
    see: log (base class); NXlog

.. _NXlog:

=====
NXlog
=====

**Status**:

  base class, extends :ref:`NXobject`, version 1.0

**Description**:

  Definition of information that is recorded against time, 
  such as information monitored during the run. 
  It contains
  the logged values and the times at which they were measured as elapsed time since a starting
  time recorded in ISO8601 format. This method of storing logged data helps to distinguish
  instances in which a variable is a dimension scale of the data, in which case it is stored
  in an ``NXdata`` group, and instances in which it is logged during the 
  run, when it should be stored in an ``NXlog`` group.
  Note: When using multiple ``NXlog`` groups, it is suggested to place 
  them inside a ``NXcollection`` group.  In such cases, when
  ``NXlog`` is used in another class,
  ``NXcollection/NXlog``  is then constructed.

**Symbols**:

  No symbol table

**Groups cited**:
  none

**Structure**:

  .. index:: time (data field)

  **time**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_TIME <NX_TIME>`}

    Time of logged entry. The times are relative to the "start" attribute 
    and in the units specified in the "units" attribute.

    .. index:: start (attribute)

    **@start**: :ref:`NX_DATE_TIME <NX_DATE_TIME>`


  .. index:: value (data field)

  **value**: :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_ANY <NX_ANY>`}

    Array of logged value, such as temperature

  .. index:: raw_value (data field)

  **raw_value**: :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_ANY <NX_ANY>`}

    Array of raw information, such as thermocouple voltage

  .. index:: description (data field)

  **description**: :ref:`NX_CHAR <NX_CHAR>`

    Description of logged value

  .. index:: average_value (data field)

  **average_value**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}


  .. index:: average_value_error (data field)

  **average_value_error**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}

    estimated uncertainty (often used: standard deviation) of average_value

  .. index:: minimum_value (data field)

  **minimum_value**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}


  .. index:: maximum_value (data field)

  **maximum_value**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}


  .. index:: duration (data field)

  **duration**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}

    Total time log was taken

**Source**:
  Automatically generated from https://github.com/nexusformat/definitions/blob/master/base_classes/NXlog.nxdl.xml