Added docs and summary

Refs #11325

Code/Mantid/Framework/PythonInterface/plugins/algorithms/CylinderPaalmanPingsCorrection.py

@@ -30,6 +30,10 @@ def category(self):
         return "Workflow\\MIDAS;PythonAlgorithms;CorrectionFunctions\\AbsorptionCorrections"
 
 
+    def summary(self):
+        return "Calculates absorption corrections for a cylindrical or annular sample using Paalman & Pings format."
+
+
     def PyInit(self):
         ws_validator = CompositeValidator([WorkspaceUnitValidator('Wavelength'), InstrumentValidator()])
 
@@ -212,6 +216,12 @@ def validateInputs(self):
         self._setup()
         issues = dict()
 
+        # Ensure that a can chemical formula is given when using a can workspace
+        if self._use_can:
+            can_chemical_formula = self.getPropertyValue('CanChemicalFormula')
+            if can_chemical_formula == '':
+                issues['CanChemicalFormula'] = 'Must provide a chemical foruma when providing a can workspace'
+
         # Ensure there are enough steps
         number_steps = int((self._sample_outer_radius - self._sample_inner_radius) / self._step_size)
         if number_steps < 20:

Code/Mantid/docs/source/algorithms/CylinderPaalmanPingsCorrection-v1.rst

@@ -0,0 +1,64 @@
+.. algorithm::
+
+.. summary::
+
+.. alias::
+
+.. properties::
+
+Description
+-----------
+
+Calculates absorption corrections for a cylindrical or annular sample giving
+output in the Paalman & Pings absorption factors: :math:`A_{s,s}` (correction
+factor for scattering and absorption in sample), :math:`A_{s,sc}` (scattering in
+sample and absorption in sample and container), :math:`A_{c,sc}` (scattering in
+container and absorption in sample and container) and  :math:`A_{c,c}`
+(scattering and absorption in container).
+
+Restrictions on the input workspace
+###################################
+
+The input workspace must have a fully defined instrument that has X axis units
+of wavelength.
+
+Usage
+-----
+
+**Example:**
+
+.. code-block:: python
+
+    # Create a sample workspace
+    sample = CreateSampleWorkspace(NumBanks=1, BankPixelWidth=1,
+                                   XUnit='Wavelength',
+                                   XMin=6.8, XMax=7.9,
+                                   BinWidth=0.1)
+
+    # Copy and scale it to make a can workspace
+    can = CloneWorkspace(InputWorkspace=sample)
+    can = Scale(InputWorkspace=can, Factor=1.2)
+
+    # Calculate absorption corrections
+    corr = CylinderPaalmanPingsCorrection(SampleWorkspace=sample,
+                                          SampleChemicalFormula='H2-O',
+                                          SampleInnerRadius=0.05,
+                                          SampleOuterRadius=0.1,
+                                          CanWorkspace=can,
+                                          CanChemicalFormula='V',
+                                          CanOuterRadius=0.15,
+                                          BeamHeight=0.1,
+                                          BeamWidth=0.1,
+                                          StepSize=0.002,
+                                          Emode='Indirect',
+                                          Efixed=1.845)
+
+    print 'Correction workspaces: %s' % (', '.join(corr.getNames()))
+
+Output:
+
+.. code-block:: none
+
+    Correction workspaces: corr_ass, corr_assc, corr_acsc, corr_acc
+
+.. categories::