Plotting Data/Models
SasView generates three different types of graph window: one that displays 1D data (i.e., \(I(Q)\) vs \(Q\)), one that displays 1D residuals (ie, the difference between the experimental data and the theory at the same \(Q\) values), and 2D color maps.
Graph window options
How to Hide-Show-Delete a graph
To expand a plot window, click the Maximise (square) icon in the top-right corner.
To shrink a plot window, click the Restore down (square-on-square) icon in the top-right corner.
To hide a plot, click the Minimise (-) icon in the top-right corner of the plot window.
To show a hidden plot, select the Restore up (square-on-square) icon on the minimised window.
To delete a plot, click the Close (x) icon in the top-right corner of the plot window.
Note
If a residuals graph (when fitting data) is hidden, it will not show up after computation.
Dragging a plot
Select the Pan (crossed arrows) icon in the toolbar at the bottom of the plot to activate this option. Move the mouse pointer to the plot. It will change to a hand. Then left-click and drag the plot around. The axis values will adjust accordingly.
To disable dragging mode, unselect the crossed arrows icon on the toolbar.
Zooming In-Out on a plot
Select the Zoom (magnifying glass) button in the toolbar at the bottom of the plot to activate this option. Move the mouse pointer to the plot. It will change to a cross-hair. Then left-click and drag the pointer around to generate a region of interest. Release the mouse button to generate the new view.
To disable zoom mode, unselect the Zoom button on the toolbar.
After zooming in on a a region, the left arrow or right arrow buttons on the toolbar will switch between recent views.
The axis range can also be specified manually. To do so go to the Graph Menu (see Invoking_the_graph_menu for further details), choose the Set Graph Range option and enter the limits in the pop box.
NOTE! If a wheel mouse is available scrolling the wheel will zoom in/out on the current plot (changing both axes). Alternatively, point at the numbers on one axis and scroll the wheel to zoom in/out on just that axis.
To return to the original view of the data, click the the Reset (home) icon in the toolbar at the bottom of the plot (see Resetting_the_graph for further details).
Saving a plot image
To save the current plot as an image file, right click on the plot to bring up the Graph Menu (see Invoking_the_graph_menu) and select Save Image. Alternatively, click on the Save (floppy disk) icon in the toolbar at the bottom of the plot.
A dialog window will open. Select a folder, enter a filename, choose an output image type, and click Save.
The currently supported image types are:
- EPS (encapsulated postscript)
- EMF (enhanced metafile)
- JPG/JPEG (joint photographics experts group)
- PDF (portable documant format)
- PNG (portable network graphics)
- PS (postscript)
- RAW/RGBA (bitmap, stored as 935x635 pixels of depth 8)
- SVG/SVGA (scalable vector graphics)
- TIF/TIFF (tagged iamge file)
Printing a plot
To send the current plot to a printer, click on the Print (printer) icon in the toolbar at the bottom of the plot.
Resetting the graph
To reset the axis range of a graph to its initial values select Reset Graph Range on the Graph Menu (see Invoking_the_graph_menu). Alternatively, use the Reset (home) icon in the toolbar at the bottom of the plot.
Modifying the graph
It is possible to make custom modifications to plots including:
- changing the plot window title
- changing the default legend location and toggling it on/off
- changing the axis label text
- changing the axis label units
- changing the axis label font & font colour
- adding/removing a text string
- adding a grid overlay
The legend and text strings can be drag and dropped around the plot
These options are accessed through the Graph Menu (see Invoking_the_graph_menu) and selecting Modify Graph Appearance (for axis labels, grid overlay and legend position) or Add Text to add textual annotations, selecting font, color, style and size. Remove Text will remove the last annotation added. To change the legend. Window Title allows a custom title to be entered instead of Graph x.
Changing scales
This menu option is only available with 1D data.
From the Graph Menu (see Invoking_the_graph_menu) select Change Scale. A dialog window will appear in which it is possible to choose different transformations of the x (usually Q) or y (usually I(Q)) axes, including:
- x, x^2, x^4, ln(x), log10(x), log10(x^4)
- y, 1/y, ln(y), y^2, y.(x^4), 1/sqrt(y),
- log10(y), ln(y.x), ln(y.x^2), ln(y.x^4), log10(y.x^4)
A View option includes short-cuts to common SAS transformations, such as:
- linear
- Guinier
- X-sectional Guinier
- Porod
- Kratky
For properly corrected and scaled data, these SAS transformations can be used to estimate, for example, Rg, rod diameter, or SANS incoherent background levels, via a linear fit (see Making_a_linear_fit).
Toggling scales
This menu option is only available with 2D data.
From the Graph Menu (see Invoking_the_graph_menu) select Toggle Linear/Log Scale to switch between a linear to log intensity scale. The type of scale selected is written alongside the colour scale.
2D color maps
This menu option is only available with 2D data.
From the Graph Menu (see Invoking_the_graph_menu) select 2D Color Map to choose a different color scale for the image and/or change the maximum or minimum limits of the scale.
Getting data coordinates
Clicking anywhere in the plot window will cause the current coordinates to be displayed in the status bar at the very bottom-left of the SasView window.
Dataset menu options
Getting data info
In the Dataset Menu (see Invoking_the_dataset_menu), highlight a data set and select DataInfo to bring up a data information dialog panel for that data set.
Saving data
In the Dataset Menu (see Invoking_the_dataset_menu), select Save Points as a File (if 1D data) or Save as a file(DAT) (if 2D data). A save dialog will appear.
1D data can be saved in either ASCII text (.TXT) or CanSAS/SASXML (.XML) formats (see Data Formats).
2D data can only be saved in the NIST 2D format (.DAT) (see Data Formats).
Making a linear fit
Linear fit performs a simple \(y(x)=ax+b\) linear fit within the plot window.
In the Dataset Menu (see Invoking_the_dataset_menu), select Linear Fit. A fitting dialog will appear. Set some initial parameters and data limits and click Fit. The fitted parameter values are displayed and the resulting line calculated from them is added to the plot.
This option is most useful for performing simple Guinier, XS Guinier, and Porod type analyses, for example, to estimate \(R_g\), a rod diameter, or incoherent background level, respectively.
The following figure shows an example of a Guinier analysis using this option
Removing data from the plot
In the Dataset Menu (see Invoking_the_dataset_menu), select Remove. The selected data will be removed from the plot.
Note
The Remove data set action cannot be undone.
Show-Hide error bars
In the Dataset Menu (see Invoking_the_dataset_menu), select Show Error Bar or Hide Error Bar to switch between showing/hiding the errors associated with the chosen dataset.
Modify plot properties
In the Dataset Menu (see Invoking_the_dataset_menu), select Modify Plot Property to change the size, color, or shape of the displayed marker for the chosen dataset, or to change the dataset label that appears in the plot legend box.
2D data averaging
Purpose
This feature is only available with 2D data.
2D data averaging allows you to perform different types of averages on your data. The region to be averaged is displayed in the plot window and its limits can be modified by dragging the boundaries around.
How to average
In the Dataset Menu (see Invoking_the_dataset_menu), select one of the following averages
- Perform Circular Average
- Sector [Q view]
- Annulus [Phi view]
- Box sum
- Box averaging in Qx
- Box averaging on Qy
A ‘slicer’ will appear (except for Perform Circular Average) in the plot that you can drag by clicking on a slicer’s handle. When the handle is highlighted in red, it means that the slicer can move/change size.
NOTE! The slicer size will reset if you try to select a region greater than the size of the data.
Alternatively, once a ‘slicer’ is active you can also select the region to average by bringing back the Dataset Menu and selecting Edit Slicer Parameters and Batch Fitting. A dialog window will appear in which you can enter values to define a region, select the number of points to plot (nbins), or apply the slicer to any or all other 2D data plots.
A separate plot window will also have appeared, displaying the requested average.
Note
The displayed average only updates when input focus is moved back to that window; ie, when the mouse pointer is moved onto that plot.
Selecting Box Sum automatically brings up the ‘Slicer Parameters’ dialog in order to display the average numerically, rather than graphically.
To remove a ‘slicer’, bring back the Dataset menu and select Clear Slicer.
Batch Slicing
A slicer can be applied to any or all existing 2D data plots using the ‘Slicer Parameters’ window. To open the window, select Edit Slicer Parameters and Batch Fitting in the Dataset Menu (see Invoking_the_dataset_menu). Batch slicing options are available at the bottom of the window.
Select the 2D plots you want to apply the slicer to. All 2D plots are selected by default. The resulting 1D data for all slicers can be saved as a text file and then sent to fitting by selecting the Auto save generated 1D check box. Sending data to the fitting perspective requires the data be saved.
Once the auto save check box is selected, you can select where the files are saved. The file name for the saved data is the slicer name plus the file name of the original data set, plus what is in the Append to file name field. The default value in the append to field includes the names and values for all of the slicer parameters.
The batch of slices can be sent to fitting if desired, with three options available. The first is to not fit the data, the second is to send the slices to individual fit pages, and the third is to send all sliced data to a single batch fit window.
Clicking Apply Slicer to Selected Plots will create a slicer for each selected plot with the parameters entered in the ‘Slicer Parameters’ window. Depending on the options selected the data may then be saved, loaded as separate data sets in the data manager panel, and finally sent to fitting.
Unmasked circular average
This operation will perform an average in constant \(Q\) rings around the (x,y) pixel location of the beam center.
Masked circular average
This operation is the same as ‘Unmasked Circular Average’ except that any masked region is excluded.
Sector average [Q View]
This operation averages in constant \(Q\) arcs.
The width of the sector is specified in degrees (\(\pm\delta|\phi|\)) each side of the central angle \(\phi\).
Annular average [\(\phi\)]
This operation performs an average between two \(Q\) values centered on (0,0), and averaged over a specified number of pixels.
The data is returned as a function of angle \(\phi\) in degrees with zero degrees at the 3 O’clock position.
Box sum
This operation performs a sum of counts in a 2D region of interest.
When editing the slicer parameters, the user can enter the length and the width the rectangular slicer and the coordinates of the center of the rectangle.
Box Averaging in Qx
This operation computes an average \(I(Q_x)\) for the region of interest.
When editing the slicer parameters, the user can control the length and the width the rectangular slicer. The averaged output is calculated from constant bins with rectangular shape. The resultant \(Q\) values are nominal values, that is, the central value of each bin on the x-axis.
Box Averaging in Qy
This operation computes an average \(I(Q_y)\) for the region of interest.
When editing the slicer parameters, the user can control the length and the width the rectangular slicer. The averaged output is calculated from constant bins with rectangular shape. The resultant \(Q\) values are nominal values, that is, the central value of each bin on the x-axis.
Note
This help document was last modified by Paul Butler, 05 September, 2016