Visualizing SED Data in Iris
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Iris Threads
Overview
Last Update: 8 Aug 2011 - updated for Iris Beta 2.5
Synopsis:
The Iris GUI is an adaptation of the Specview (STScI) spectral visualization and analysis GUI, and as a result is equipped with many of the data display preferences offered by that application. This thread presents the various options available for customizing the SED data display in Iris.
Note: As most Specview features remain unchanged between the standard and the Sherpa-enabled Iris version, the documentation provided in the Specview help documentation serves as an exhaustive reference for most of the data visualization features in Iris.
Contents
- Introduction
- Setting Display Preferences
- Coplotting Multiple Spectrograms
- Displaying Metadata and Data Values
- History
Introduction
As each SED data file is read into Iris, it is automatically displayed in the tool's main window, where you can interact with the plot in various ways. Options for customizing the data display are provided both in the Iris menu bar and within the main display; these are described below.
Setting Display Preferences
Adjusting the coordinates view port
The set of widgets in the upper-left corner of the data display are available for adjusting the view and orientation of the SED segment(s) within the main display.
![[Iris screenshot image]](./imgs/widgets.png)
Refreshing the Data Plot
Preferences Menu Options
![[Iris screenshot image]](./imgs/menu_bar.png)
The Iris Preferences menu contains many options for customizing the data plot in the Iris display, such as choosing preferred units for the x and y axes; setting cursor style and size; selecting graphics colors; among many other options. The list of self-explanatory options in the Preferences->Edit Preferences window is shown below; refer to the Specview documentation for a description of each.
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Units
The preferred units for the data display, e.g., "ergs/cm2/s/angstrom" versus "angstrom", may be set via the "Units" button in the main display.
![[Iris screenshot image]](./imgs/set_units.png)
Axis Scale
The scale of the data plot axes in the Iris main display can be changed using the "Plot Type" button, or by clicking the cursor near any one of the four corners of the display; this will open a small window in which the X and Y axes scale may be set to linear or logarithmic (regular or extended).
You can also set a preference to specify that data plots should automatically display with logarithmic scaling by checking the "XAutoLog" and "YAutoLog" boxes in the Preferences->Edit Preferences window (or by using the "Auto log scale" option in the Iris Preferences pull-down menu).
Grid
Selecting the "Grid" option in the main display overlays a coordinate grid onto the main plot.
![[Iris screenshot image]](./imgs/grid.png)
Coplotting Multiple Spectrograms
The Iris menu bar contains the Display option for selecting a previously read spectrogram from the tool's memory buffer for display in the main plot area of Iris, or in a separate, secondary display. The Coplot menu option allows you to select one or multiple spectrograms for plotting or coplotting in the main plot area, respectively.
![[Iris screenshot image]](./imgs/menu_bar.png)
When the Coplot option is selected, a "Spectrograms in memory" window opens in which more than one data set entry may be selected, using the mouse cursor plus the Shift or Control key.
![Iris GUI snapshot[]](./imgs/spec_in_mem.png)
Clicking the "Plot/Coplot" button will plot all selected data sets simultaneously in the Iris main display, if their physical units are deemed compatible by Iris's internal units conversion mechanism. The resulting plot will be displayed and stored in the memory buffer as "Coplot".
![Iris GUI snapshot[]](./imgs/coplot_zoom_pan.png)
Note that the coplotting process does not involve combining, coadding, or splicing the spectral data in memory in any way; the raw data from the multiple input spectrograms is completely preserved in the resulting combination. This means that two separate SED data segments loaded into Iris for a particular source - e.g., observed with two differeny observatories and spanning separate (or overlapping) spectral ranges - may be offset from one another, as Iris does not scale, trim, and join the separate segments to form a seamless SED for the source.
The Pan option at the bottom of the Iris main display allows you to view the full spectral range covered by all SED data which has been read into the session, beyond the edges of the data segment which is currently displayed.
![[Iris screenshot image]](./imgs/coplot_pan_only.png)
Displaying Metadata and Data Values
Right-clicking the cursor over a data segment or point in the plot will bring up a window with various tabs containing associated metadata information, as well as the independent and dependent data arrays (or point). Selecting the "Coplot" menu option and then right-clicking on a filename in the window that appears, allows you to simultaneously view the metadata for all points loaded from the chosen file.
![[Iris screenshot]](./imgs/all_metadata.png)
![[Iris screenshot]](./imgs/all_data.png)
The metadata information associated with a data segment or point includes many details, such as segment type, e.g., "SPECTRUM" or "Photometry Point"; data identification, e.g., the instrument used to obtain the data, in which observing mode, and the bandpass covered by the data; curation information such as the publisher of the data, e.g., Hopkins Ultraviolet Telescope, and the rights to the data, whether "PUBLIC" or not; among many other details.
The x and y data values shown for a data segment are referred to as the "Spectral Axis" and "Flux Axis", respectively, and reflect the values as they were imported into Iris from NED or uploaded from a file on your hard disk - i.e., not what is currently plotted in the Iris display (in the event that you changed the units of the data plot within the display). For example, if the data were uploaded in Jansky flux units versus frequency in Hertz, but then you change the display units to ergs/s/cm2/Angstrom versus Angstrom, the data point values returned will be in Jansky flux units and Hertz.
History
08 Aug 2011 | updated for Iris Beta 2.5 |