Session 2. DAWN Training - Advanced Data Browsing
Welcome to the second in a series of training sessions to use the DAWN software suite. The aims of this tutorial are :
Further features of the plotting system, annotations and regions
The plot tool system
Plotting tools for 1D data
Plotting tools for 2D data
Expressions in the Data Browsing perspective
History tools
1. The Plot - Customizing
This section gives a brief introduction to a final few aspects of the plotting system before starting to use the tool system.
Annotations
Annotations allow you to make notes on a plot referring to a particular region of a trace or image.
Open the file MoKegde_1_15.dat and plot In(I0/It) vs Energy, open the View menu and select Add Annotation (refer to tutorial 1 if you are not sure how to do this).
The Add Annotation dialog will appear, give your annotation a name and click OK.
Drag the Annotation label around and the cross marking where the Annotation meets the trace. Edit your Annotation using the Settings action on the plot (or by right-clicking on the annotation and selecting Configure)
Exercise 1. open the file pow_M99S5_1_0001.cbf and add an Annotation to the image. What extra information does the Annotation have here compared to the trace annotation?
Regions of Interest (ROIs)
Region selections are heavily use by the Plot Tool system for selecting areas of a trace/image to be analyzed. They can also be used outside of the tool system for marking interesting areas.
Open the View menu, go to Selection Region and select add line selection.
You should notice the mouse cursor has changed. Click the mouse once to start drawing the line and again to finish.
After the line is drawn, click on and hold to move it or change its start and end positions.
Exercise 2. Draw some of the other regions (Box, Sector...), how many clicks does it take to draw a Sector, and what does each click define?
Exercise 3. Change the color of the regions you have drawn (where might you be able to do this)?
After creating some regions remove them by either (a) right-clicking on a region and selecting delete or (b) using the remove region plot toolbar actions
2. Plotting Tools
The tool system is used to extract extra information from plotted data, whether it is fitting a peak to a trace, or integrating an area on a image. Since traces and images represent very different kinds of data, there are different sets of tools for each type.
Plotting tools are a special type of view that are connected to the plot they were opened on (this is a bit of a generalization but we will get on to that later in the section on History Tools).
Image Tools (or 2D tools)
DAWN includes a comprehensive set of image analysis tools which tends to get longer with every release. The first set of tools were are going to look at are the Profile tools.
Profile tools
Open or switch to file powder diffraction image, remove any annotations or ROIs that may be on it.
Click the Plot Tools drop down action and select Line Profile, the Line Profile Tool view will open and the mouse cursor changes to the Draw ROI cursor (as in the previous section).
Draw a Line ROI on the plot, see how the profile appears in the tool view. Move the line ROI and watch the plot update.
Click the Create New Profile action on the Tool views plotting toolbar and draw another line ROI
Each Profile tool will have this action in the same location on the toolbar and is the easiest way to draw the correct ROI for each profile tool.
Exercise 4. Remove the ROIs from the plot and try some of the other profile tools (Box Profile, Radial Profile...)
Exercise 5. Try the Zoom Profile Tool, how is this different from the other Profile Tools?
The nice thing about the Profile Tools is that you can use the Trace Tools on the profiles they create (more on this later).
Masking Tool
From investigating the powder diffraction image you may have noticed that the gap between the detector plates leaves steps in the profile which can affect further data analysis. The Masking Tool can be used to mask out these areas removing there effect from the profile.
Clear the powder diffraction image of any ROIs and open the Radial Profile Tool. Draw the sector as close to the centre of the circles as possible. Notice the dips in the data where the edges of the detector plates interfere with the profile.
Open the Masking Tool, select Enable lower mask, click Apply. A green mask will appear over the gaps between the plates.
Re-open the Radial Profile Tool, notice how the dips in the profile are gone.
Exercise 6. Try the other options in the Masking tool to build up your mask (Direct Draw, Regions).
Exercise 7. Export your mask to file, clear you current mask, then import it again.
Color mapping Tool
In the last tutorial we saw how DAWN automatically sets the Contrast/Brightness (histogram) of an image and that the auto-histogramming method can be selected and tailored in the settings menu.
Sometimes finer adjustment of the image histogram is needed and that is what the Colour Mapping tools is for.
Exercise 8. Open the Colormap tool, change the colormap and use some of the various methods to adjust the image.
Exercise 9. How do you reset the histogram?
The Lock action at the top of the Color Mapping tool can be use to fix the histogram over the current range for all images shown. This is useful seeing how the absolute values of the image intensity varies through an image stack.