DataComparison.rst

Data Comparison
===============

.. contents:: Table of Contents
  :local:

Overview
--------

.. interface:: Data Comparison
  :align: right

The data comparison interface provides a method of comparing the spectra of
multiple :ref:`MatrixWorkspace <MatrixWorkspace>` (either pre loaded into
Mantid or loaded via the interface its self) using a preview plot.

Note that data in this plot is not normalised to bin width as it is by default
in Mantid plot windows, to reduce plotting artefacts you may want to consider
running :ref:`ConvertToDistribution <algm-ConvertToDistribution>` prior to
loading the data into the UI.

Add Data
--------

.. interface:: Data Comparison
  :widget: gbAddData
  :align: right

This allows new data to be added to the comparison, this can be added by either
selecting a :ref:`MatrixWorkspace <MatrixWorkspace>` alrady loaded into Mantid
or by selecting a file to load.

Alternatively you can select a :ref:`WorkspaceGroup <WorkspaceGroup>` to load
it's contents into the UI.

Once the data has been selected the *Add Data* button can be used to add it to
the comparison, this will add a curve to the preview plot and assign it the next
unused colour for the curve (if all are in use then black will be used).

Data Table
----------

.. interface:: Data Comparison
  :widget: gbCurrentData
  :align: right

The data table shows a list of the current data shown on the plot including the
workspace name and currently plotted spectrum index. This also allows the curve
colour to be changed manually.

This also allows a spectrum index offset to be set on a per workspace basis,
this allows workspaces to be aligned relative to each other in the venet that
the spectra that you want to compare do not have the same spectrum index in each
workspace.

The value of the offset for a workspace defines the spectrum index that the
first spectum will line up to relative to the spectrum selection spin box. At
least one offset value must be zero (this is set check for automatically after
an offset value has been changed).

View
----

.. interface:: Data Comparison
  :widget: gbView
  :align: right

The view section contains a set of tools for manipulating the plot and selecting
spectra to plot via the *Spectrum* spin box, this is shown as the current
spectra index out of the maximum spectra index after the offsets are applied.

The *Pan* and *Zoom* buttons are usd to enable and disable the pan and zoom
tools; pan allows you to drag the plot area to show a specific section of the
curves, zoom allows you to select a section of the curves to zoom in on and
reset the zoom level by right clicking on the plot, when either tool is selected
you can use the scroll wheel to change the zoom level when the mouse is over the
plot area.

The *Maintain Zoom Level* option is used to keep the same pan and zoom settings
when switching between spectra and adding new data, when this is disabled the
plot will automatically be resized such that all curves are visible on the plot.
This can also be done manually by clicking the *Reset View* button.

Diff
----

.. interface:: Data Comparison
  :widget: gbDiff
  :align: right

A diff spectra of two workspaces can be created by selecting two workspaces in
the data table (by holding Ctrl whilst making a selection) and clicking the *Diff
Selected* button, this will subtract the current spectra for the second workspace
selected from the current spectra for the first spectra selected and plot the
result spectra as a green curve on the plot.

If either of the diff workspaces are removed then the diff will be cleared. If
one of the workspaces can no longer be displayed as it is offset from the other
workspace then a messsage will be displayed in the diff tool and no plot will be
shown, however the diff will continue to function once both workspaces can be
displayed again.

The diff workspace is created by running :ref:`ExtractSignleSpectrum
<algm-ExtractSingleSpectrum>` on the two data workspaces, the second of which is
then rebinned to match the binning of the first using :ref:`RebinToWorkspace
<algm-RebinToWorkspace>` and then using :ref:`Minus <algm-Minus>` to calculate
the difference.

Note that if the two diffed workspaces have different binning, then the second
one selected will be rebinned to match the first before the diff is created.
This will not modify the data in the otiginal workspace.

.. categories:: Interfaces General