Doc Update: Polydispersity in Sasmodels

[smk78]

This PR attempts to address some of the documentation deficiencies in SasView raised in SasView/sasview#1839. It is complemented by PR SasView/sasview#1938.

The usage text regarding the array distribution has been tweaked and clarified.

[pkienzle]

Text is okay as is.

The Suggested Applications suggestion says to use uniform for orientation, but you can also use gaussian if 3σ is small enough. Better would be to move Maier-Saupe and/or Cyclic gaussian from examples/weights to sasmodels/weights.py, or at least mention that they can be added as user-defined distributions (and add them to the marketplace?)

What we call the Boltzmann distribution in sasmodels/weights.py is in fact a Laplace distribution. Boltzmann is a limiting case with no shift, no negative values, and scale related to temperature. We could mention in the docs that it is the Laplace distribution, but I don't think we want to change the name in the code. The distribution I put in example/weights/laplace.py isn't Laplace since its scale is b rather than 1/b.

[smk78]

@pkienzle commented:

Better would be to move Maier-Saupe and/or Cyclic gaussian from examples/weights to sasmodels/weights.py, or at least mention that they can be added as user-defined distributions (and add them to the marketplace?)

If we put the Maier-Saupe and Cyclic_gaussian distributions on the Marketplace, how would you use them from SasView?

[pkienzle]

According to the docs you need to save the file into ~/.sasview/weights.

Note that we probably need to change the way distributions are defined if we implement #486, but I don't expect that to happen any time soon.

[smk78]

@pkienzle commented:

According to the docs you need to save the file into ~/.sasview/weights.

Oops. My bad! I should have read our wonderful docs! Just tested this and it works! Fantastic! The 'plugin' distribution appears in the Function drop-down and can be used like the in-program distributions.

I'm just going to push a minor doc edit for the benefit of Windows users though.

[smk78]

@pkienzle commented:

What we call the Boltzmann distribution in sasmodels/weights.py is in fact a Laplace distribution. Boltzmann is a limiting case with no shift, no negative values, and scale related to temperature. We could mention in the docs that it is the Laplace distribution, but I don't think we want to change the name in the code. The distribution I put in example/weights/laplace.py isn't Laplace since its scale is b rather than 1/b.

Have now mentioned this in the docs:

Have also created several in-doc links to save scrolling. And for consistency have linked more references (some were, some weren't).

[smk78]

@pkienzle commented:

Better would be to move Maier-Saupe and/or Cyclic gaussian from examples/weights to sasmodels/weights.py, or at least mention that they can be added as user-defined distributions (and add them to the marketplace?)

Have mentioned these distributions in the doc and will also create/populate a Distributions category on the Marketplace.

[smk78]

Maier-Saupe & Cyclic Gaussian now added to Marketplace.

[wpotrzebowski]

ready for testing on OSX

[wpotrzebowski]

sasmodels ready for testing on OSX

[wpotrzebowski]

sasmodels ready for testing on OSX