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MatrixWorkspace with Python

MatrixWorkspaces are the most frequently used workspace type in Mantid. The two most commonly used implementations are Workspace2D and Event Workspace. A Workspace2D stores the data in either a histogram form (most commonly) or as point data for each spectrum, whereas an Event Workspace stores a list of raw observations against each spectrum. More detail can be found by looking at the individual workspace pages for these workspace types.

Working with MatrixWorkspaces

Loading a Workspace2D and extracting some basic details:

ws2D = Load(Filename="LOQ49886.nxs")

# Basic queries
print("Number of histograms: " + str(ws2D.getNumberHistograms()))
print("Is histogram data: " + str(ws2D.isHistogramData()))
print("Number of bins: " + str(ws2D.blocksize()))

# More advanced queries
spectrumAxis = ws2D.getAxis(1)
print("Is spectra axis: " + str(spectrumAxis.isSpectra()))
print("Number of spectra: " + str(spectrumAxis.length()))

xAxis = ws2D.getAxis(0)
xUnit = xAxis.getUnit()
print("X-Unit: "  + str(xUnit.unitID() + ', ' + xUnit.caption() + ', ' + str(xUnit.symbol())))

# Get x-axis data as a NumPy array
xData = ws2D.readX(9683)
print("X-Data type: " + str(type(xData)))
print("X-Data:")
print(xData)

# Get y-axis data and error data
print("Y-Data:")
print(ws2D.readY(9683))
print("E-Data:")
print(ws2D.readE(9683))

# Looping over each spectrum and obtaining a read-only reference to the counts
for i in range(ws2D.getNumberHistograms()):
    counts = ws2D.readY(i)

Working with EventWorkspaces

Loading a Workspace checking it’s type, and reading the number of events.

eventWS = Load(Filename="CNCS_7860_event.nxs")
print("Type of Workspace: ", eventWS.id())
print("EventWorkspace called %s contains %s events" %(eventWS.name(), eventWS.getNumberEvents()))

Rebinning EventWorkspaces

rebinned = Rebin(InputWorkspace=eventWS,Params='1000')
rebinnedToWorkspace2D = Rebin(InputWorkspace=eventWS,Params='1000', PreserveEvents=False)