| 1 | '''This is a fit to data.nxs using the convolution of a resolution and a DiffRotDiscreteCircle function. |
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| 2 | The data and resolution correspond to an experiment of Octa-Methyl Silsesquioxane molecules |
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| 3 | carried out at 200K |
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| 4 | |
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| 5 | data.nxs is such that the optimized parameters should be: |
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| 6 | |
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| 7 | Intensity = 0.745, Radius = 0.876(Angstroms), Decay = 763.6(pico-seconds) |
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| 8 | |
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| 9 | In DiffRotDiscreteCircle, "N" and "Q " are attributes, not fitting parameters. |
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| 10 | Data corresponds to Q=1.9. This is a fit to methyl rotations, thus N-3 was selected |
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| 11 | |
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| 12 | I chose starting parameters in "fitstring" reasonable far apart from |
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| 13 | the optimal values. Feel free to change this initial guess. |
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| 14 | |
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| 15 | The units for this example are: |
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| 16 | [Intensity] = arbitray units |
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| 17 | [Radius] = Angstroms |
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| 18 | [Decay] = pico-seconds |
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| 19 | [X-values in data.nxs] = micro-eV |
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| 20 | |
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| 21 | ''' |
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| 22 | data = LoadNexus(Filename='/tmp/data.nxs') |
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| 23 | elastic = LoadNexus(Filename='/tmp/resolution.nxs') |
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| 24 | fitstring='(composite=Convolution,FixResolution=true,NumDeriv=true;name=TabulatedFunction,FileName="",Workspace=resolution,Scaling=1;(name=DiffRotDiscreteCircle,N=3,NumDeriv=true,Q=1.9,Intensity=1,Radius=1,Decay=10));name=LinearBackground,A0=0.001,A1=0.0001' |
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| 25 | Fit(Function=fitstring, InputWorkspace='data', CreateOutput=1) |
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