.. algorithm::

.. summary::

.. relatedalgorithms::

.. properties::

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

CalculateDIFC calculates the value of :math:`DIFC` for every pixel in
an instrument.

.. math:: DIFC = \frac{m_n}{h} \frac{(L_1 + L_2) 2 \sin(\theta)}{1 + {offset}}

Or if OffsetMode is `Signed` :math:`DIFC` will be calculated with the following equation
for logarithmically binned data:

.. math:: DIFC = \frac{m_n}{h} \cdot (L1 + L2) 2 \sin(\theta) \cdot (1+|BinWidth|)^{-offset}

DIFC is used in the equation

.. math:: TOF = DIFC \times d

This algorithm uses the same underlying calculation as :ref:`algm-ConvertUnits`
and :ref:`algm-AlignDetectors`.

When specifying the ``CalibrationWorkspace``, this algorithm copies the
values in the ``detid`` and ``difc`` columns of the calibration workspace.
It ignores any other calibration constants, such as ``difa`` and
``tzero`` (for more information, see the :ref:`DiffractionCalibrationWorkspace` concept page).

Assumptions: There are no assumptions and this algorithm works on the results
of :ref:`algm-LoadEmptyInstrument`.

Usage
-----

**Example - CalculateDIFC**

.. testcode:: CalculateDIFCExample

   ws = LoadEmptyInstrument(Filename="NOMAD_Definition.xml", OutputWorkspace="ws")
   ws = CalculateDIFC(ws, OutputWorkspace="ws")

   # Print the result
   print("The output workspace has {} spectra".format(ws.getNumberHistograms()))
   print("DIFC of pixel {} is {:.0f}".format(100, ws.readY(100)[0]))

Output:

.. testoutput:: CalculateDIFCExample

  The output workspace has 101376 spectra
  DIFC of pixel 100 is 1274

**Determining traditional offsets**

.. code-block:: python

   ws = LoadEmptyInstrument(Filename="NOMAD_Definition.xml", OutputWorkspace="ws")
   LoadDiffCal(InputWorkspace=ws, Filename='NOM_cal.h5', WorkspaceName='NOM')
   uncalibrated = CalculateDIFC(ws, OutputWorkspace="uncalibrated")
   calibrated = CalculateDIFC(ws, CalibrationWorkspace="NOM_cal", OutputWorkspace="calibrated")

   offsets = calibrated/uncalibrated - 1.

.. categories::

.. sourcelink::