.. fitting_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. .. |beta| unicode:: U+03B2 .. |gamma| unicode:: U+03B3 .. |mu| unicode:: U+03BC .. |sigma| unicode:: U+03C3 .. |phi| unicode:: U+03C6 .. |theta| unicode:: U+03B8 .. |chi| unicode:: U+03C7 .. |inlineimage004| image:: sm_image004.gif .. |inlineimage005| image:: sm_image005.gif .. |inlineimage008| image:: sm_image008.gif .. |inlineimage009| image:: sm_image009.gif .. |inlineimage010| image:: sm_image010.gif .. |inlineimage011| image:: sm_image011.gif .. |inlineimage012| image:: sm_image012.gif .. |inlineimage018| image:: sm_image018.gif .. |inlineimage019| image:: sm_image019.gif Fitting Perspective =================== Load_a_File_ Single_Fit_ Simultaneous_Fitting_ Batch_Fitting_ Model_Selection_ Model_Category_Manager_ Model_Functions_ Custom_Model_Editor_ Polydispersity_Distributions_ Smearing_Computation_ Polarisation_Magnetic_Scattering_ Key_Combinations_ Status_Bar_Help_ .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Load_a_File: Load a File ----------- From Menu go to *Data* -> *Load Data File(or Folder)* . Select a file/folder from the menu bar and click on Open button. Data contained in the file will be displayed. To cancel the loading click on *cancel* . In case a file can not be loaded, an error message will be displayed on the statusbar. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Single_Fit: Single Fit ---------- One of two fit-engines can be chosen from the Fitting menu bar. The Simple Fit- engine uses Scipy's leasqr and the Complex Fit-Engine is a custom optimizer that provides a better chance to find the global minimum of the |chi| 2 but that requires longer computation time. In order to set a data to a control panel (FitPage), see the "DataLoader Help". Once a data set to the FiPage, select a model from the combo box. The default parameters of the model will be display. Set initial parameters if need. Check and uncheck parameters to fit/fix. Click the *'Fit'* button. When the fitting is finished, the resultant parameter values will be displayed with the errors. If a error is missing, it generally means that the corresponding parameter is not very depending on the model. The chisq/Npt_fit and the plot associated with the fit operation will be also updated. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Simultaneous_Fitting: Simultaneous Fitting -------------------- This fitting option enables to set a number of the constraints between the parameters of fitting(s). It requires one or more FitPages with a data and a model set for the fitting, and performs multiple fittings given by the FitPage(s). The Complex (ParkMC) FitEngine will be used automatically. Simultaneous Fit without Constraint Assuming some FitPages are already set up, check the checkboxes of the model_data rows to fit. And click the 'Fit' button. The results will return to each FitPages. Note that the chi2/Npts returned is the sum of the chi2/Npts of each fits. If one needs the chi2 value only for a page, click the 'Compute' button in the FitPage to recalculate. Simultaneous Fit with Constraint Enter constraint in the text control next to *constraint fit* button. Constraint should be of type model1 parameter name = f(model2 parameter name) for example, M0.radius=2*M1.radius. Many constraints can be entered for a single fit. Each of them should be separated by a newline charater or ";" The easy setup can generate many constraint inputs easily when the selected two models are the same type. Note that the chi2/Npts returned is the sum of the chi2/Npts of each fits. If one needs the chi2 value only for one fit, click the 'Compute' button in the FitPage to recalculate. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Batch_Fitting: Batch Fitting ------------- Batch_Fit_ Batch_Window_ Edit_Grid_ Save_Grid_ Open_Batch_Results_ Plot_ View_Column_Cell_ .. _Batch_Fit: Batch Fit --------- Create a *Batch Page* by selecting the *Batch* radio button on the DataExplorer (see figure below) and for a new control page select 'New FitPage' in the Fitting menubar. .. image:: batch_button_area.bmp Figure 1: MenuBar: Load Data to the DataExplorer if not already loaded. Select one or more data sets by checking the check boxes, and then make sure that "Fitting" is selected in the dropdown menu next to the "Send To" button. Once ready, click the 'Send To' button to set data to a BatchPage. If already an empty batch page exists, it will be set there. Otherwise it will create a new Batch Page. Set up the model and the parameter values as same as a single fitting (see Single Fit help) . Then use 'Fit' button to perform the fitting. Unlike a single fit, the results of the fittings will not return to the BatchPage'. Instead, a Grid window will be provided once the fitting is completed. The Grid window is also accessible from the 'View' menu (see Figure 2). Note that only one model is used for all the data. The initial parameter values given in the control page will be used all the data fittings. If one wants the FitEngine to use the initial values from the results of the previous data fitting (if any), choose the 'Chain Fitting' option in the Fitting menubar, which will speed up the fitting especially when you have lots of, and similar, data sets. .. _Batch_Window: Batch Window ------------ Batch Window provides an easy way to view the fit results, i.e., plot data, fits, and residuals. Batch window will be automatically shown after a batch fit is finished. Once closed, it can be opened anytime from the "View" menubar item (see Figure 2). .. image:: restore_batch_window.bmp Figure 2: Edit Menu: .. _Edit_Grid: Edit Grid --------- Once a batch fit is completed, all fitted and fixed model parameters are displayed to the current sheet of the batch window except the errors of the parameters. To view the errors, click on a given column then under *Edit* menubar item, and insert the desired parameter by selecting a menu item with the appropriated label. Empty column can be inserted in the same way. A column value can be customized by editing an existing empty column. To Remove column from the grid, select it, choose edit menu, and click the *'remove'* menu item. Any removed column should reinserted whenever needed. All above options are also available when right clicking on a given column label(see Figure 3). *Note:* A column always needs to be selected in order to remove or insert a column in the grid. .. image:: edit_menu.bmp Figure 3: Edit Menu: .. _Save_Grid: Save Grid --------- To save the current page on the batch window, select the *'File'* menubar item(see Figure 4), then choose the *'Save as'* menu item to save it as a .csv file. *Note:* The grid doesn't save the data array, fits, and the array residuals. As a result, the 'View (fit) Results' functionality will be lost when reloading the saved file. Warning! To ensure accuracy of saved fit results, it is recommended to save the current grid before modifying it . .. _Open_Batch_Results: Open Batch Results ------------------ Any *csv* file can be opened in the grid by selecting the *'Open'* under the *'File'* menu in the Grid Window(see Figure 4). All columns in the file will be displayed but insertion will not available. Insertion will be available only when at least one column will be removed from the grid. .. image:: file_menu.bmp Figure 4: MenuBar: .. _Plot: Plot ---- To *plot* a column versus another, select one column at the time, click the *'Add'* button next to the text control of X/Y -axis *Selection Range* to plot the value of this column on the X/Y axis. Alternatively, all available range can be selected by clicking the column letter (eg. B). Repeat the same procedure the next axis. Finally, click the *'Plot'* button. When clicking on *Add* button, the grid will automatically fill the axis label, but different labels and units can be entered in the correct controls before clicking on the plot button. *X/Y -Axis Selection Range* can be edited manually. These text controls allow the following types of expression (operation can be + - * /, or pow) 1) if the current axis label range is a function of 1 or more columns, write this type of expression constant1 * column_name1 [minimum row index : maximum row index] operator constant2 * column_name2 [minimum row index : maximum row index] Example: radius [2 : 5] -3 * scale [2 : 5] 2) if only some values of a given column are need but the range between the first row and the last row used is not continuous, write the following expression in the text control column_name1 [minimum row index1 : maximum row index1] , column_name1 [minimum row index2 : maximum row index2] Example : radius [2 : 5] , radius [10 : 25] Note: Both text controls ( X and Y-axis Selection Ranges) need to be filled with valid entries for plotting to work. The dY-bar is optional (see Figure 5). .. image:: plot_button.bmp Figure 5: Plotting .. _View_Column_Cell: View Column/Cell(s) ------------------- Select 1 or more cells from the same column, click the 'View Fits' button to display available curves. For example, select the cells of the 'Chi2' column, then click the 'View Fits' button. The plots generates will represent the residuals plots. If you select any cells of the 'Data' column and click the 'View Fits' button. It generates both data and fits in the graph (see Figure 6). Alternatively, just click the column letter (eg. B) to choose all the available data sets, then simply click the 'View Fits' button to plot the data and fits. .. image:: view_button.bmp Figure 6: View Fits .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Model_Selection: Model_Type_ Change_Model_Parameters_ Write_your_Own_Model_ .. _Model_Type: Model Type ---------- Models are grouped into three classes * *Shapes* * *Shape-Independent* * *Uncategorised* * *Customized Models* * *Structure Factor* .. _Change_Model_Parameters: Change Model Parameters ----------------------- To visualize model in a different window, from menu click on *Model*. Select a type of model and then the name of your model.A new window will appear with the plot of your model with default values. Change model's parameters on *model view* tab and view the plotted model with its new parameters. .. _Write_your_Own_Model: Write your Own Model -------------------- The custom model editors are provided from 'Fitting' menu in the menu bar. See 'Custom model editor' in the side menu on left. Advanced users can write your own model and save it (in .py format) into *plugin_models* directory in .sasview of your home directory (eg., username\.sasview>\plugin_models). Your plugin model will be added into "<>Customized Models" on the next model selection. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Model_Category_Manager: Model Category Manager ---------------------- Our SAS models are, by default, classified into 5 categories; shapes, shape-independent, structure factor, and customized models, where these categories (except the customized models) can be reassigned, added, and removed using 'Category Manager'. Each models can also be enabled(shown)/ disabled(hidden) from the category that they belong. The Category Manager panel is accessible from the model category 'Modify' button in the fitting panel or the 'View/Category Manager' menu in the menu bar (Fig. 1). 1) Enable/Disable models: Check/uncheck the check boxes to enable/disable the models (Fig. 2). 2) Change category: Highlight a model in the list by left-clicking and click the 'Modify' button. In the 'Change Category' panel, one can create/use a category for the model, then click the 'Add' button. In order to delete a category, select a category name and click the 'Remove Selected' button (Fig. 3). 3) To apply the changes made, hit the OK button. Otherwise, click the 'Cancel' button (Fig. 2). .. image:: cat_fig0.bmp Fig.1 .. image:: cat_fig1.bmp Fig.2 .. image:: cat_fig2.bmp Fig.3 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Model_Functions: Model Functions --------------- Model Documentation .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Custom_Model_Editor: Custom Model Editor ------------------- Description_ New_ Sum_Multi_p1_p2_ Advanced_ Delete_ .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Description: Description ----------- This menu (Fitting/Edit Custom Model in the menu bar) interface is to provide you an easy way to write your own custom models. The changes in a model function are effective after it is re-selected from the combo-box menu. .. image:: edit_model_menu.bmp .. _New: New --- This option is used to make a new model. A model code generated by this option can be viewed and further modified by the 'Advanced' option below. .. image:: new_model.bmp .. _Sum_Multi_p1_p2: Sum|Multi(p1,p2) ---------------- This option create a new sum (or multiplication) model. Fill up the (sum model function) name and the description. The description will show up on details button in the application. Then select the p1 or p2 model for the sum/multi model, select an operator as necessary and click the Apply button for activation. Hit the 'Close' button when it's done. .. image:: sum_model.bmp .. _Advanced: Advanced -------- The menu option shows all the files in the plugin_models folder. You can edit, modify, and save it. It is recommended to modify only the lines with arrow (-------). In the end of edit, 'Compile' and 'Run' from the menu bar to activate or to see the model working properly. .. _Delete: Delete ------ The menu option is to delete the custom models. Just select the file name to delete. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Polydispersity_Distributions: Polydispersity Distributions ---------------------------- Calculates the form factor for a polydisperse and/or angular population of particles with uniform scattering length density. The resultant form factor is normalized by the average particle volume such that P(q) = scale*\/Vol + bkg where F is the scattering amplitude and the\<\>denote an average over the size distribution. Users should use PD (polydispersity: this definition is different from the typical definition in polymer science) for a size distribution and Sigma for an angular distribution (see below). Note that this computation is very time intensive thus applying polydispersion/ angular distrubtion for more than one paramters or increasing Npts values might need extensive patience to complete the computation. Also note that even though it is time consuming, it is safer to have larger values of Npts and Nsigmas. The following five distribution functions are provided * *Rectangular_Distribution_* * *Array_Distribution_* * *Gaussian_Distribution_* * *Lognormal_Distribution_* * *Schulz_Distribution_* .. _Rectangular_Distribution: Rectangular Distribution ------------------------ .. image:: pd_image001.png The xmean is the mean of the distribution, w is the half-width, and Norm is a normalization factor which is determined during the numerical calculation. Note that the Sigma and the half width *w* are different. The standard deviation is .. image:: pd_image002.png The PD (polydispersity) is .. image:: pd_image003.png .. image:: pd_image004.jpg .. _Array_Distribution: Array Distribution ------------------ This distribution is to be given by users as a txt file where the array should be defined by two columns in the order of x and f(x) values. The f(x) will be normalized by SasView during the computation. Example of an array in the file 30 0.1 32 0.3 35 0.4 36 0.5 37 0.6 39 0.7 41 0.9 We use only these array values in the computation, therefore the mean value given in the control panel, for example ‘radius = 60’, will be ignored. .. _Gaussian_Distribution: Gaussian Distribution --------------------- .. image:: pd_image005.png The xmean is the mean of the distribution and Norm is a normalization factor which is determined during the numerical calculation. The PD (polydispersity) is .. image:: pd_image003.png .. image:: pd_image006.jpg .. _Lognormal_Distribution: Lognormal Distribution ---------------------- .. image:: pd_image007.png The /mu/=ln(xmed), xmed is the median value of the distribution, and Norm is a normalization factor which will be determined during the numerical calculation. The median value is the value given in the size parameter in the control panel, for example, “radius = 60�. The PD (polydispersity) is given by /sigma/ .. image:: pd_image008.png For the angular distribution .. image:: pd_image009.png The mean value is given by xmean=exp(/mu/+p2/2). The peak value is given by xpeak=exp(/mu/-p2). .. image:: pd_image010.jpg This distribution function spreads more and the peak shifts to the left as the p increases, requiring higher values of Nsigmas and Npts. .. _Schulz_Distribution: Schulz Distribution ------------------- .. image:: pd_image011.png The xmean is the mean of the distribution and Norm is a normalization factor which is determined during the numerical calculation. The z = 1/p2– 1. The PD (polydispersity) is .. image:: pd_image012.png Note that the higher PD (polydispersity) might need higher values of Npts and Nsigmas. For example, at PD = 0.7 and radisus = 60 A, Npts >= 160, and Nsigmas >= 15 at least. .. image:: pd_image013.jpg .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Smearing_Computation: Smearing Computation -------------------- Slit_Smearing_ Pinhole_Smearing_ 2D_Smearing_ .. _Slit_Smearing: Slit Smearing ------------- The sit smeared scattering intensity for SAS is defined by .. image:: sm_image002.gif where Norm = .. image:: sm_image003.gif Equation 1 The functions |inlineimage004| and |inlineimage005| refer to the slit width weighting function and the slit height weighting determined at the q point, respectively. Here, we assumes that the weighting function is described by a rectangular function, i.e., .. image:: sm_image006.gif Equation 2 and .. image:: sm_image007.gif Equation 3 so that |inlineimage008| |inlineimage009| for |inlineimage010| and u. The |inlineimage011| and |inlineimage012| stand for the slit height (FWHM/2) and the slit width (FWHM/2) in the q space. Now the integral of Equation 1 is simplified to .. image:: sm_image013.gif Equation 4 Numerical Implementation of Equation 4 -------------------------------------- Case 1 ------ For |inlineimage012| = 0 and |inlineimage011| = constant. .. image:: sm_image016.gif For discrete q values, at the q values from the data points and at the q values extended up to qN= qi + |inlineimage011| the smeared intensity can be calculated approximately .. image:: sm_image017.gif Equation 5 |inlineimage018| = 0 for *Is* in *j* < *i* or *j* > N-1*. Case 2 ------ For |inlineimage012| = constant and |inlineimage011| = 0. Similarly to Case 1, we get |inlineimage019| for qp= qi- |inlineimage012| and qN= qi+ |inlineimage012|. |inlineimage018| = 0 for *Is* in *j* < *p* or *j* > *N-1*. Case 3 ------ For |inlineimage011| = constant and |inlineimage011| = constant. In this case, the best way is to perform the integration, Equation 1, numerically for both slit height and width. However, the numerical integration is not correct enough unless given a large number of iteration, say at least 10000 by 10000 for each element of the matrix, W, which will take minutes and minutes to finish the calculation for a set of typical SAS data. An alternative way which is correct for slit width << slit hight, is used in SasView. This method is a mixed method that combines method 1 with the numerical integration for the slit width. .. image:: sm_image020.gif Equation 7 for qp= qi- |inlineimage012| and qN= qi+ |inlineimage012|. |inlineimage018| = 0 for *Is* in *j* < *p* or *j* > *N-1*. .. _Pinhole_Smearing: Pinhole Smearing ---------------- The pinhole smearing computation is done similar to the case above except that the weight function used is the Gaussian function, so that the Equation 6 for this case becomes .. image:: sm_image021.gif Equation 8 For all the cases above, the weighting matrix *W* is calculated when the smearing is called at the first time, and it includes the ~ 60 q values (finely binned evenly) below (\>0) and above the q range of data in order to cover all data points of the smearing computation for a given model and for a given slit size. The *Norm* factor is found numerically with the weighting matrix, and considered on *Is* computation. .. _2D_Smearing: 2D Smearing ----------- The 2D smearing computation is done similar to the 1D pinhole smearing above except that the weight function used was the 2D elliptical Gaussian function .. image:: sm_image022.gif Equation 9 In Equation 9, x0 = qcos/theta/ and y0 = qsin/theta/, and the primed axes are in the coordinate rotated by an angle /theta/ around the z-axis (below) so that x’0= x0cos/theta/+y0sin/theta/ and y’0= -x0sin/theta/+y0cos/theta/. Note that the rotation angle is zero for x-y symmetric elliptical Gaussian distribution. The A is a normalization factor. .. image:: sm_image023.gif Now we consider a numerical integration where each bins in /theta/ and R are *evenly* (this is to simplify the equation below) distributed by /delta//theta/ and /delta/R, respectively, and it is assumed that I(x’, y’) is constant within the bins which in turn becomes .. image:: sm_image024.gif Equation 10 Since we have found the weighting factor on each bin points, it is convenient to transform x’-y’ back to x-y coordinate (rotating it by -/theta/ around z axis). Then, for the polar symmetric smear .. image:: sm_image025.gif Equation 11 where .. image:: sm_image026.gif while for the x-y symmetric smear .. image:: sm_image027.gif Equation 12 where .. image:: sm_image028.gif Here, the current version of the SasView uses Equation 11 for 2D smearing assuming that all the Gaussian weighting functions are aligned in the polar coordinate. In the control panel, the higher accuracy indicates more and finer binnng points so that it costs more in time. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Polarisation_Magnetic_Scattering: Polarisation/Magnetic Scattering -------------------------------- Magnetic scattering is implemented in five (2D) models * *SphereModel* * *CoreShellModel* * *CoreMultiShellModel* * *CylinderModel* * *ParallelepipedModel* In general, the scattering length density (SLD) in each regions where the SLD (=/beta/) is uniform, is a combination of the nuclear and magnetic SLDs and depends on the spin states of the neutrons as follows. For magnetic scattering, only the magnetization component, *M*perp, perpendicular to the scattering vector *Q* contributes to the the magnetic scattering length. .. image:: mag_vector.bmp The magnetic scattering length density is then .. image:: dm_eq.gif where /gamma/ = -1.913 the gyromagnetic ratio, /mu/B is the Bohr magneton, r0 is the classical radius of electron, and */sigma/* is the Pauli spin. For polarised neutron, the magnetic scattering is depending on the spin states. Let's consider that the incident neutrons are polarized parallel (+)/ anti-parallel (-) to the x' axis (See both Figures above). The possible out-coming states then are + and - states for both incident states Non-spin flips: (+ +) and (- -) Spin flips: (+ -) and (- +) .. image:: M_angles_pic.bmp Now, let's assume that the angles of the *Q* vector and the spin-axis (x') against x-axis are /phi/ and /theta/up, respectively (See Figure above). Then, depending upon the polarisation (spin) state of neutrons, the scattering length densities, including the nuclear scattering length density (/beta/N) are given as, for non-spin-flips .. image:: sld1.gif for spin-flips .. image:: sld2.gif where .. image:: mxp.gif .. image:: myp.gif .. image:: mzp.gif .. image:: mqx.gif .. image:: mqy.gif Here, the M0x, M0y and M0z are the x, y and z components of the magnetization vector given in the xyz lab frame. The angles of the magnetization, /theta/M and /phi/M as defined in the Figure (above) .. image:: m0x_eq.gif .. image:: m0y_eq.gif .. image:: m0z_eq.gif The user input parameters are M0_sld = DMM0, Up_theta = /theta/up, M_theta = /theta/M, and M_phi = /phi/M. The 'Up_frac_i' and 'Up_frac_f' are the ratio (spin up)/(spin up + spin down) neutrons before the sample and at the analyzer, respectively. *Note:* The values of the 'Up_frac_i' and 'Up_frac_f' must be in the range between 0 and 1. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Key_Combinations: Key Combinations ---------------- Copy_Paste_ Bookmark_ Graph_Context_Menu_ FTolerance_ .. _Copy_Paste: Copy & Paste ------------ To copy the parameter values in a Fit(Model) panel to the clipboard: *Ctrl(Cmd on MAC) + Left(Mouse)Click* on the panel. To paste the parameter values to a Fit(Model)panel from the clipboard: *Ctrl(Cmd on MAC) + Shift + Left(Mouse)Click* on the panel. If this operation is successful, it will say so in the info line at the bottom of the SasView window. .. _Bookmark: Bookmark -------- Bookmark of a fit-panel or model-panel status: *(Mouse)Right-Click* and select the bookmark in the popup list. .. _Graph_Context_Menu: Graph Context Menu ------------------ To get the graph context menu to print, copy, save data, (2D)average, etc.: *Locate the mouse point on the plot to highlight and *(Mouse) Right Click* to bring up the full menu. .. _FTolerance: FTolerance (SciPy) ------------------ To change the ftol value of the Scipy FitEngine (leastsq): First, make sure that the Fit panel has data and a model selected. *Ctrl(Cmd on MAC) + Shift + Alt + Right(Mouse)Click* on the panel. Then, set up the value in the dialog panel. If this operation is successful, the new ftol value will be displayed in the info line at the bottom of the SV window.Note that increasing the ftol value may cause for the fitting to terminate with higher |chi| sq. .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ .. _Status_Bar_Help: Status Bar Help --------------- Message_Warning_Hint_ Console_ .. _Message_Warning_Hint: Message/Warning/Hint -------------------- The status bar located at the bottom of the application frame, displays messages, hints, warnings and errors. .. _Console: Console ------- Select *light bulb/info icon* button in the status bar at the bottom of the application window to display available history. During a long task, the console can also help users to understand the status in progressing.