Changeset db1d9d5 in sasmodels for doc/guide/resolution.rst

Timestamp:

Mar 28, 2019 5:16:51 PM (6 years ago)

Author:

Paul Kienzle <pkienzle@…>

Branches:

master, ticket-1257-vesicle-product, ticket_1156, ticket_822_more_unit_tests

Children:

8795b6f

Parents:

a34b811

Message:

merge with master

File:

• doc/guide/resolution.rst (modified) (3 diffs)

doc/guide/resolution.rst

@@ -1 @@
-.. sm_help.rst
-
-.. This is a port of the original SasView html help file to ReSTructured text
-.. by S King, ISIS, during SasView CodeCamp-III in Feb 2015.
+.. resolution.rst
+
+.. This is a port of the original SasView html help file sm_help to ReSTructured
+.. text by S King, ISIS, during SasView CodeCamp-III in Feb 2015.
 
 
@@ -17 +17 @@
 resolution contribution into a model calculation/simulation (which by definition
 will be exact) to make it more representative of what has been measured
-experimentally - a process called *smearing*. Sasmodels does the latter.
+experimentally - a process called *smearing*. The Sasmodels component of SasView
+does the latter.
 
 Both smearing and desmearing rely on functions to describe the resolution
@@ -29 +30 @@
 for the instrument and stored with the data file.  If not, they will need to
 be set manually before fitting.
+
+.. note::
+    Problems may be encountered if the data set loaded by SasView is a
+    concatenation of SANS data from several detector distances where, of
+    course, the worst Q resolution is next to the beam stop at each detector
+    distance. (This will also be noticeable in the residuals plot where
+    there will be poor overlap). SasView sensibly orders all the input
+    data points by increasing Q for nicer-looking plots, however, the dQ
+    data can then vary considerably from point to point. If 'Use dQ data'
+    smearing is selected then spikes may appear in the model fits, whereas
+    if 'None' or 'Custom Pinhole Smear' are selected the fits look normal.
+
+    In such instances, possible solutions are to simply remove the data
+    with poor Q resolution from the shorter detector distances, or to fit
+    the data from different detector distances simultaneously.