.. algorithm::

.. summary::

.. relatedalgorithms::

.. properties::

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

Converts the representation of the vertical axis of a
:ref:`MatrixWorkspace <MatrixWorkspace>` from its default of holding the
spectrum number to the target unit given - theta, elastic Q, elastic
Q^2 or elastic d-spacing.

The spectra will be reordered in increasing order by default, however this can be disabled by `OrderAxis=False`.
In the case of the latter, spectra will preserve correspondence to the original workspace.
The new unit and duplicates will not be aggregated. Any spectrum for which a detector is
not found (i.e. if the instrument definition is incomplete) will not
appear in the output workspace.

InPlane2Theta and SignedInPlane2Theta return the 2theta value of the projection of the pixel on the horizontal scattering plane.


Usage
-----

**Example: Convert vertical axis to theta**

.. testcode::

   # Creates a workspace with some detectors attached
   dataws = CreateSampleWorkspace(NumBanks=1,BankPixelWidth=2) # 2x2 detector

   theta = ConvertSpectrumAxis(dataws, Target="Theta")

   vertical_axis = theta.getAxis(1)
   print("There are {} axis values".format(vertical_axis.length()))
   print("Final theta value: {:.6f} (degrees)".format(vertical_axis.getValue(vertical_axis.length() - 1)))

.. testoutput::

   There are 4 axis values
   Final theta value: 0.129645 (degrees)

**Example: Convert vertical axis to elastic Q for direct geometry**

.. testcode::

   # Creates a workspace with some detectors attached
   dataws = CreateSampleWorkspace(NumBanks=1,BankPixelWidth=2) # 2x2 detector

   qws = ConvertSpectrumAxis(dataws, Target="ElasticQ", EFixed=15., EMode="Direct")

   vertical_axis = qws.getAxis(1)
   print("There are {} axis values".format(vertical_axis.length()))
   print("Final Q value: {:.6f} (A^-1)".format(vertical_axis.getValue(vertical_axis.length() - 1)))

.. testoutput::

   There are 4 axis values
   Final Q value: 0.006088 (A^-1)

.. categories::

.. sourcelink::