dep: Deprecate characteristic functions containing camel case

docs/examples/coreshellnp.py

@@ -73,10 +73,13 @@ def makeRecipe(stru1, stru2, datname):
     # and a spherical shell CF for the shell. Since this is set up as two
     # phases, we implicitly assume that the core-shell correlations contribute
     # very little to the PDF.
-    from diffpy.srfit.pdf.characteristicfunctions import shellCF, sphericalCF
+    from diffpy.srfit.pdf.characteristicfunctions import (
+        shell_particle,
+        spherical_particle,
+    )
 
-    contribution.register_function(sphericalCF, name="f_CdS")
-    contribution.register_function(shellCF, name="f_ZnS")
+    contribution.register_function(spherical_particle, name="f_CdS")
+    contribution.register_function(shell_particle, name="f_ZnS")
 
     # Write the fitting equation. We want to sum the PDFs from each phase and
     # multiply it by a scaling factor.

docs/examples/crystalpdf.py

@@ -93,16 +93,17 @@ def makeRecipe(ciffile, datname):
 
     # We start by constraining the phase to the known space group. We could do
     # this by hand, but there is a method in diffpy.srfit.structure named
-    # 'constrainAsSpaceGroup' for this purpose. The constraints will by default
-    # be applied to the sites, the lattice and to the ADPs. See the method
-    # documentation for more details. The 'constrainAsSpaceGroup' method may
-    # create new Parameters, which it returns in a SpaceGroupParameters object.
-    from diffpy.srfit.structure import constrainAsSpaceGroup
+    # 'constrain_as_space_group' for this purpose. The constraints will by
+    # default be applied to the sites, the lattice and to the ADPs. See the
+    # method documentation for more details. The 'constrain_as_space_group'
+    # method may create new Parameters, which it returns in a
+    # SpaceGroupParameters object.
+    from diffpy.srfit.structure import constrain_as_space_group
 
-    sgpars = constrainAsSpaceGroup(phase, "Fm-3m")
+    sgpars = constrain_as_space_group(phase, "Fm-3m")
 
-    # The SpaceGroupParameters object returned by 'constrainAsSpaceGroup' holds
-    # the free Parameters allowed by the space group constraints. Once a
+    # The SpaceGroupParameters object returned by 'constrain_as_space_group'
+    # holds the free Parameters allowed by the space group constraints. Once a
     # structure is constrained, we need (should) only use the Parameters
     # provided in the SpaceGroupParameters, as the relevant structure
     # Parameters are constrained to these.

docs/examples/crystalpdfobjcryst.py

@@ -84,7 +84,7 @@ def makeRecipe(ciffile, datname):
     # constraints get enforced within the ObjCrystCrystalParSet. Free
     # Parameters are stored within the 'sgpars' member of the
     # ObjCrystCrystalParSet, which is the same as the object returned from
-    # 'constrainAsSpaceGroup'.
+    # 'constrain_as_space_group'.
     #
     # As before, we have one free lattice parameter ('a'). We can simplify
     # things by iterating through all the sgpars.

docs/examples/nppdfcrystal.py

@@ -56,9 +56,9 @@ def makeRecipe(ciffile, grdata):
     pdfcontribution.add_profile_generator(pdfgenerator)
 
     # Register the nanoparticle shape factor.
-    from diffpy.srfit.pdf.characteristicfunctions import sphericalCF
+    from diffpy.srfit.pdf.characteristicfunctions import spherical_particle
 
-    pdfcontribution.register_function(sphericalCF, name="f")
+    pdfcontribution.register_function(spherical_particle, name="f")
 
     # Now we set up the fitting equation.
     pdfcontribution.set_equation("f * G")

docs/examples/simplepdf.py

@@ -48,9 +48,9 @@ def makeRecipe(ciffile, datname):
     # Configure the fit variables
     phase = contribution.nickel.phase
 
-    from diffpy.srfit.structure import constrainAsSpaceGroup
+    from diffpy.srfit.structure import constrain_as_space_group
 
-    sgpars = constrainAsSpaceGroup(phase, "Fm-3m")
+    sgpars = constrain_as_space_group(phase, "Fm-3m")
 
     for par in sgpars.latpars:
         recipe.add_variable(par)

news/cf-non-physical-input.rst

@@ -0,0 +1,27 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* Change the characteristic functions in ``diffpy.srfit.pdf.characteristicfunctions`` to emit a ``RuntimeWarning`` when a non-physical shape parameter makes them return zero, since a zero return flattens the fit residual and stalls a refinement without any other sign to the user. The warning is issued once per process for each distinct problem so a refinement loop does not repeat it.
+* Change ``lognormal_spherical_particle`` in ``diffpy.srfit.pdf.characteristicfunctions`` to return zero for a negative ``particle_diameter_sigma`` instead of silently returning ``spherical_particle``. A ``particle_diameter_sigma`` of zero is still the sphere limit.
+* Change ``sheet_particle`` in ``diffpy.srfit.pdf.characteristicfunctions`` to return an array of zeros for a non-positive ``sheet_thickness`` when ``r`` is an array, instead of a scalar zero.
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* Fix ``shell_particle`` in ``diffpy.srfit.pdf.characteristicfunctions`` returning a smoothly varying branch of unphysical values, some below negative one, for a negative ``thickness`` or ``radius``, which a refinement could mistake for a real solution. It now returns zero.
+* Fix ``shell_particle`` in ``diffpy.srfit.pdf.characteristicfunctions`` returning one at every ``r`` for a zero ``thickness``, where the normalizing denominator vanishes. It now returns zero.
+* Fix ``spheroidal_particle`` in ``diffpy.srfit.pdf.characteristicfunctions`` raising ``ZeroDivisionError`` for a zero ``equatorial_radius``. It now returns zero.
+
+**Security:**
+
+* <news item>

news/characteristicfunctions-dep.rst

@@ -0,0 +1,25 @@
+**Added:**
+
+* Add ``spherical_particle``, ``spheroidal_particle``, ``lognormal_spherical_particle``, ``sheet_particle``, and ``shell_particle`` to ``diffpy.srfit.pdf.characteristicfunctions``, replacing ``sphericalCF``, ``spheroidalCF``, ``lognormalSphericalCF``, ``sheetCF``, and ``shellCF``.
+* Add ``constrain_as_space_group`` to ``diffpy.srfit.structure.sgconstraints``, replacing ``constrainAsSpaceGroup``.
+
+**Changed:**
+
+* Change ``spheroidalCF2`` and ``shellCF2`` in ``diffpy.srfit.pdf.characteristicfunctions`` to be deprecated aliases that convert their arguments and call ``spheroidal_particle`` and ``shell_particle``, instead of separate implementations.
+
+**Deprecated:**
+
+* Deprecate ``sphericalCF``, ``spheroidalCF``, ``spheroidalCF2``, ``lognormalSphericalCF``, ``sheetCF``, ``shellCF``, and ``shellCF2`` in ``diffpy.srfit.pdf.characteristicfunctions``.
+* Deprecate ``constrainAsSpaceGroup`` in ``diffpy.srfit.structure.sgconstraints``.
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

src/diffpy/__init__.py

@@ -15,3 +15,6 @@
 # See LICENSE.rst for license information.
 #
 ##############################################################################
+from pkgutil import extend_path
+
+__path__ = extend_path(__path__, __name__)