.. auto-generated by script ../../../../utils/nxdl2rst.py from the NXDL source 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**:

  Information recorded as a function of time.

  Description 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 :ref:`NXdata` group, and instances in which it is logged during the 
  run, when it should be stored in an :ref:`NXlog` group.
  Note: When using multiple :ref:`NXlog` groups, it is suggested to place 
  them inside a :ref:`NXcollection` group.  In such cases, when
  :ref:`NXlog` is used in another class,
  :ref:`NXcollection`/:ref:`NXlog` is then constructed.

**Symbols**:

  No symbol table

**Groups cited**:
  none

**Structure**:

  .. index:: time (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 (field attribute)

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


  .. index:: value (field)

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

    Array of logged value, such as temperature

  .. index:: raw value (field)

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

    Array of raw information, such as thermocouple voltage

  .. index:: description (field)

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

    Description of logged value

  .. index:: average value (field)

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


  .. index:: average value error (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 (field)

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


  .. index:: maximum value (field)

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


  .. index:: duration (field)

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

    Total time log was taken

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