ConvertSpectrumAxis v2

../_images/ConvertSpectrumAxis-v2_dlg.png

ConvertSpectrumAxis dialog.

Summary

Converts the axis of a Workspace2D which normally holds spectrum numbers to one of Q, Q^2 or theta. ‘Note’: After running this algorithm, some features will be unavailable on the workspace as it will have lost all connection to the instrument. This includes things like the 3D Instrument Display.

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace Mandatory The name of the input workspace.
OutputWorkspace Output MatrixWorkspace Mandatory The name to use for the output workspace.
Target Input string Mandatory The unit to which spectrum axis is converted to - “theta” (for the angle in degrees), Q or Q^2, where elastic Q is evaluated at EFixed. Note that ‘theta’ and ‘signed_theta’ are there for compatibility purposes; they are the same as ‘Theta’ and ‘SignedTheta’ respectively. Allowed values: [‘Theta’, ‘SignedTheta’, ‘ElasticQ’, ‘ElasticQSquared’, ‘theta’, ‘signed_theta’]
EMode Input string Direct Some unit conversions require this value to be set (“Direct” or “Indirect”). Allowed values: [‘Direct’, ‘Indirect’]
EFixed Input number Optional Value of fixed energy in meV : EI (EMode=Direct) or EF (EMode=Indirect))

Description

Converts the representation of the vertical axis (the one up the side of a matrix in MantidPlot) of a Workspace2D from its default of holding the spectrum number to the target unit given - theta, elastic Q and elastic Q^2.

The spectra will be reordered in increasing order by 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.

Usage

Example: Convert vertical axis to theta

# 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 %d axis values" % vertical_axis.length()
print "Final theta value: %f (degrees)" % vertical_axis.getValue(vertical_axis.length() - 1)
There are 4 axis values
Final theta value: 0.129645 (degrees)

Example: Convert vertical axis to elastic Q for direct geometry

# 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 %d axis values" % vertical_axis.length()
print "Final Q value: %f (A^-1)" % vertical_axis.getValue(vertical_axis.length() - 1)
There are 4 axis values
Final Q value: 0.006088 (A^-1)

Categories: Algorithms | Transforms\Units | Transforms\Axes