Changes in / [b09aee8:39a018b] in sasview

Location:

src/sas/sasgui/perspectives

Files:

• calculator/model_editor.py (modified) (2 diffs)
• fitting/fitpage.py (modified) (2 diffs)
• fitting/media/fitting_help.rst (modified) (5 diffs)
• fitting/media/residuals_help.rst (modified) (3 diffs)

src/sas/sasgui/perspectives/calculator/model_editor.py

@@ -391 +391 @@
         self._msg_box.SetLabel(msg)
         self._msg_box.SetForegroundColour(color)
-        self._set_model_list()
         if self.parent.parent is not None:
             from sas.sasgui.guiframe.events import StatusEvent
@@ -433 +432 @@
         if len(main_list) > 1:
             main_list.sort()
-        self.model1.Clear()
-        self.model2.Clear()
         for idx in range(len(main_list)):
             self.model1.Append(str(main_list[idx]), idx)

src/sas/sasgui/perspectives/fitting/fitpage.py

@@ -365 +365 @@
         # StaticText for chi2, N(for fitting), Npts + Log/linear spacing
         self.tcChi = BGTextCtrl(self, wx.ID_ANY, "-", size=(75, 20), style=0)
-        self.tcChi.SetToolTipString("Chi2/DOF (DOF=Npts-Npar fitted)")
+        self.tcChi.SetToolTipString("Chi2/Npts(Fit)")
         self.Npts_fit = BGTextCtrl(self, wx.ID_ANY, "-", size=(75, 20), style=0)
         self.Npts_fit.SetToolTipString(
@@ -391 +391 @@
         self.points_sizer.Add(self.pointsbox)
 
-        box_description_1 = wx.StaticText(self, wx.ID_ANY, 'Reduced Chi2')
+        box_description_1 = wx.StaticText(self, wx.ID_ANY, '   Chi2/Npts')
         box_description_2 = wx.StaticText(self, wx.ID_ANY, 'Npts(Fit)')
 

src/sas/sasgui/perspectives/fitting/media/fitting_help.rst

@@ -426 +426 @@
 See :ref:`Assessing_Fit_Quality`.
 
-The objective of model-fitting is to find a *physically-plausible* model, and
-set of model parameters, that generate a theory that reproduces the experimental
-data and minimizes the values of the residuals.
+The objective of model-fitting is to find a *physically-plausible* model, and set
+of model parameters, that generate a theory that reproduces the experimental data
+and gives residual values as close to zero as possible.
 
 Change the default values of the model parameters by hand until the theory line
-starts to represent the experimental data. Then check the tick boxes alongside
-the 'background' and 'scale' parameters. Click the *Fit* button. SasView
-will optimise the values of the 'background' and 'scale' and also display the
-corresponding uncertainties on the optimised values.
-
-.. note::
-   If the uncertainty on a fitted parameter is unrealistically large, or if it
-   displays as NaN, the model is most likely a poor representation of the data,
-   the parameter in question is highly correlated with one or more of the other
-   fitted parameters, or the model is relatively insensitive to the value of
-   that particular parameter.
-
-In the bottom left corner of the *Fit Page* is a box displaying a normalised
-value of the statistical $\chi^2$ parameter (the reduced $\chi^2$,
-See :ref:`Assessing_Fit_Quality`) returned by the optimiser.
+starts to represent the experimental data. Then uncheck the tick boxes alongside
+all parameters *except* the 'background' and the 'scale'. Click the *Fit* button.
+SasView will optimise the values of the 'background' and 'scale' and also display
+the corresponding uncertainties on the optimised values.
+
+*NB: If no uncertainty is shown it generally means that the model is not very*
+*dependent on the corresponding parameter (or that one or more parameters are*
+*'correlated').*
+
+In the bottom left corner of the *Fit Page* is a box displaying the normalised value
+of the statistical $\chi^2$ parameter returned by the optimiser.
 
 Now check the box for another model parameter and click *Fit* again. Repeat this
-process until all relevant parameters are checked and have been optimised. As
-the fit of the theory to the experimental data improves, the value of 'Reduced
-Chi2' will decrease. A good model fit should produce values of Reduced Chi2
-close to one, and certainly << 100. See :ref:`Assessing_Fit_Quality`.
+process until most or all parameters are checked and have been optimised. As the
+fit of the theory to the experimental data improves the value of 'chi2/Npts' will
+decrease. A good model fit should easily produce values of 'chi2/Npts' that are
+close to one, and certainly <100. See :ref:`Assessing_Fit_Quality`.
 
 SasView has a number of different optimisers (see the section :ref:`Fitting_Options`).
@@ -466 +462 @@
 *the Data Explorer is checked (see the section* :ref:`Loading_data` *).*
 
-This mode is an extension of the :ref:`Single_Fit_Mode` that allows for some
-relatively extensive constraints between fitted parameters in a single *FitPage*
-or between several *FitPage*'s (eg, to constrain all fitted parameters to be the
-same in a contrast series of *FitPages* except for the solvent sld parameter,
-constrain the length to be twice that of the radius in a single *FitPage*,
-fix the radius of the sphere in one *FitPage* to be the same as the radius of
-the cylinder in a second *FitPage*, etc).
+This mode is an extension of the :ref:`Single_Fit_Mode` that fits two or more data
+sets *to the same model* simultaneously. If necessary it is possible to constrain
+fit parameters between data sets (eg, to fix a background level, or radius, etc).
 
 If the data to be fit are in multiple files, load each file, then select each file
@@ -509 +501 @@
 next to *Add Constraint?* in the *Fit Constraints* box.
 
-To constrain all identically named parameters to fit *simultaneously* to the
-same value across all the *Fitpages* use the *Easy Setup* drop-down buttons in
-the *Const & Simul Fit* page.
-
 *NB: You can only constrain parameters that are set to refine.*
+
+When ready, click the *Fit* button on the *Const & Simul Fit* page, NOT the *Fit*
+button on the individual *FitPage*'s.
+
+Simultaneous Fits without Constraints
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The results of the model-fitting will be returned to each of the individual
+*FitPage*'s.
+
+Note that the chi2/Npts value returned is the SUM of the chi2/Npts of each fit. To
+see the chi2/Npts value for a specific *FitPage*, click the *Compute* button at the
+bottom of that *FitPage* to recalculate. Also see :ref:`Assessing_Fit_Quality`.
+
+Simultaneous Fits with Constraints
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Use the *Easy Setup* drop-down buttons in the *Const & Simul Fit* page to set
+up constraints between *FitPage*'s.
 
 Constraints will generally be of the form
@@ -528 +535 @@
 Many constraints can be entered for a single fit.
 
-When ready, click the *Fit* button on the *Const & Simul Fit* page, NOT the *Fit*
-button on the individual *FitPage*'s.
-
 The results of the model-fitting will be returned to each of the individual
 *FitPage*'s.
 
-Note that the Reduced Chi2 value returned is the SUM of the Reduced Chi2 of
-each fit. To see the Reduced Chi2 value for a specific *FitPage*, click the 
-*Compute* button at the bottom of that *FitPage* to recalculate. Note that in
-doing so the degrees of freedom will be set to Npts.
-See :ref:`Assessing_Fit_Quality`.  Moreover in the case of constraints the
-degrees of freedom are less than one might think due to those constraints.
+Note that the chi2/Npts value returned is the SUM of the chi2/Npts of each fit. To
+see the chi2/Npts value for a specific *FitPage*, click the *Compute* button at the
+bottom of that *FitPage* to recalculate. Also see :ref:`Assessing_Fit_Quality`.
 
 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
@@ -765 +766 @@
 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
 
-.*Document History*
-
-| 2017-09-10 Paul Butler
-| 2017-09-15 Steve King
-| 2018-03-05 Paul Butler
+.. note::  This help document was last changed by Paul Butler, 10 September
+   2017

src/sas/sasgui/perspectives/fitting/media/residuals_help.rst

@@ -27 +27 @@
 
 $\chi^2$ is a statistical parameter that quantifies the differences between
-an observed data set and an expected dataset (or 'theory') calculated as
+an observed data set and an expected dataset (or 'theory').
+
+When showing the a model with the data, *SasView* displays this parameter
+normalized to the number of data points, $N_\mathrm{pts}$ such that
 
 .. math::
 
-  \chi^2
-  =  \sum[(Y_i - \mathrm{theory}_i)^2 / \mathrm{error}_i^2]
+  \chi^2_N
+  =  \sum[(Y_i - \mathrm{theory}_i)^2 / \mathrm{error}_i^2] / N_\mathrm{pts}
 
-Fitting typically minimizes the value of $\chi^2$.  For assessing the quality of
-the model and its "fit" however, *SasView* displays the traditional reduced
-$\chi^2_R$ which normalizes this parameter by dividing it by the number of
-degrees of freedom (or DOF). The DOF is the number of data points being
-considered, $N_\mathrm{pts}$, reduced by the number of free (i.e. fitted)
-parameters, $N_\mathrm{par}$. Note that model parameters that are kept fixed do
-*not* contribute to the DOF (they are not "free"). This reduced value is then
-given as
+When performing a fit, *SasView* instead displays the reduced $\chi^2_R$,
+which takes into account the number of fitting parameters $N_\mathrm{par}$
+(to calculate the number of 'degrees of freedom'). This is computed as
 
 .. math::
@@ -49 +47 @@
   / [N_\mathrm{pts} - N_\mathrm{par}]
 
-Note that this means the displayed value will vary depending on the number of
-parameters used in the fit. In particular, when doing a calculation without a
-fit (e.g. manually changing a parameter) the DOF will now equal $N_\mathrm{pts}$
-and the $\chi^2_R$ will be the smallest possible for that combination of model,
-data set, and set of parameter values.
-
-When $N_\mathrm{pts} \gg N_\mathrm{par}$ as it should for proper fitting, the
-value of the reduced $\chi^2_R$ will not change very much.
+The normalized $\chi^2_N$ and the reduced $\chi^2_R$ are very close to each
+other when $N_\mathrm{pts} \gg N_\mathrm{par}$.
 
 For a good fit, $\chi^2_R$ tends to 1.
@@ -98 +90 @@
 | 2015-06-08 Steve King
 | 2017-09-28 Paul Kienzle
-| 2018-03-04 Paul Butler