| 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 | Intensity = 0.74, Radius = 2.25, Diffusion = 0.024 |
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| 7 | After the fit, check workspace data_Parameters for f1.f1 parameters |
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| 8 | |
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| 9 | The units for this example are: |
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| 10 | [Intensity] = arbitray units |
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| 11 | [Radius] = Angstroms |
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| 12 | [Diffusion] = Anstroms^2 / pico-seconds |
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| 13 | [X-values in data.nxs] = mili-eV |
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| 14 | ''' |
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| 15 | |
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| 16 | workdir = '/tmp' |
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| 17 | LoadNexus(Filename='{0}/data.nxs'.format( workdir), OutputWorkspace='data' ) |
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| 18 | LoadNexus(Filename='{0}/resolution.nxs'.format( workdir), OutputWorkspace='resolution' ) |
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| 19 | |
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| 20 | #The fitstring defines the model: A * Elastic + B*Convolution( Elastic, DiffSphere) + LinearBackground |
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| 21 | fitstring='name=TabulatedFunction,Workspace=resolution,WorkspaceIndex=0,Scaling=0.02,constraints=(0.0001<Scaling);(composite=Convolution,FixResolution=true,NumDeriv=true;name=TabulatedFunction,Workspace=resolution,WorkspaceIndex=0,Scaling=1;(name=DiffSphere,NumDeriv=true,Q=1.0,Intensity=0.2,Radius=4.0,Diffusion=0.05));name=LinearBackground,A0=0.0,A1=-0.0' |
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| 22 | |
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| 23 | Fit(Function=fitstring, InputWorkspace='data', StartX=-0.1, EndX=0.1, CreateOutput=1) |
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