.. algorithm::

.. summary::

.. relatedalgorithms::

.. properties::

Description
-----------

The algorithm LoadNexusProcessed will read a Nexus data file created
by :ref:`algm-SaveNexusProcessed` or :ref:`algm-SaveNexusESS` and place the data into the named workspace. The file name can be an absolute or relative path and
should have the extension .nxs, .nx5 or .xml.

.. warning::
	Using XML format can be extremely slow for large data sets and generate very
	large files.

The optional parameters can be used to control which spectra are
loaded into the workspace. If SpectrumMin and SpectrumMax are given,
then only that range to data will be loaded. A specific list of
spectra to load can also be given (SpectrumList). Filtering of spectra
is supported when loading into workspaces of type :ref:`Workspace2Ds
<Workspace2D>` and also :ref:`EventWorkspaces <EventWorkspace>`.


A Mantid Nexus file may contain several workspace entries each labelled
with an integer starting at 1. By default the highest number workspace
is read, earlier ones can be accessed by setting the EntryNumber.

If the saved data has a reference to an XML file defining instrument
geometry this will be read.

This is version 2 of the algorithm. Information about the previous behaviour can be found in :ref:`algm-SaveNexusProcessed-v1`, which does not handle :ref:`algm-SaveNexusESS` outputs. This is the only difference between the two versions.

Time series data
################

The log data in the Nexus file (NX\_LOG sections) is loaded as
TimeSeriesProperty data within the workspace. Time is stored as seconds
from the Unix epoch. Only floating point logs are stored and loaded at
present.

Child algorithms used
#####################

The Child Algorithms used by LoadMuonNexus are:

-  LoadInstrument - this algorithm looks for an XML description of the
   instrument and if found reads it.

Usage
-----

**Example**

.. testcode:: LoadNexusProcessedex

    import os

    #Create an absolute path by joining the proposed filename to a directory
    #os.path.expanduser("~") used in this case returns the home directory of the current user
    savePath = os.path.expanduser("~")
    wsPath = os.path.join(savePath, "LoadNexusProcessedTest.nxs")

    ws = CreateSampleWorkspace(WorkspaceType="Histogram", NumBanks=2, BankPixelWidth=1, BinWidth=10, Xmax=50)
    SaveNexusProcessed(ws, wsPath)

    wsOutput = LoadNexusProcessed(wsPath)

    print(CompareWorkspaces(ws,wsOutput, CheckInstrument=False)[0])

    os.remove(wsPath)

Output:

.. testoutput:: LoadNexusProcessedex

   True

.. testcode:: SaveNexusESSExample

    from mantid.simpleapi import *
    import os
    import tempfile
    simple_run = CreateSampleWorkspace(NumBanks=2, BankPixelWidth=10)
    destination = os.path.join(tempfile.gettempdir(), "sample_processed.nxs")
    SaveNexusESS(Filename=destination, InputWorkspace=simple_run)
    ws = LoadNexusProcessed(Filename=destination)
    print("Workspace includes {} detectors".format(ws.detectorInfo().size(), 2 * 10 * 10))
    os.remove(destination)

Output:

.. testoutput:: SaveNexusESSExample

  Workspace includes 200 detectors

.. categories::

.. sourcelink::