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: http://www.adass.org/adass/proceedings/adass02/P3-2/
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IRSA has extended and adapted PtPlot to provide a rich suite of user-controlled functions for modifying the appearance and attributes of plots, such as symbol, color, plot boundaries, data limits, plot annotations, etc. It supports interactive conversion between logarithmic and linear scales, as well as reversal of axes. This modified package, QtPlot, supports column delimited ASCII format tables (the so-called IPAC table format), but of greater importance is the fact that it supports XML structured for astronomical plot directives, underpinned by the eXtensible Data Format(XDF), a container for transporting scientific data. The XML support also supports plotting by reference to a path to a data file.
QtPlot has been deployed operationally as an applet at IRSA, where it supports interactive plotting of spectra from the Submillimeter Wave Astronomical Satellite (SWAS), and light curves from the American Association of Variable Star Observers (AAVSO). It has also been integrated into the On-Line Archive Science Information Service (OASIS), IRSA's primary data fusion toolkit, for general two dimensional plotting support (e.g., plotting two columns of a table retrieved from a database). It can access local files or remote files, through HTTP protocols, and can be directly called by a web application.
The QtPlot package contains classes, applets, and applications for two dimensional graphical display of data. It can be used as an independent Java package, or it can be called by another Java package which manages passing arguments, controls input parameters, and handles opening or closing plots on the screen. Furthermore, QtPlot can graphically display data on web pages when deployed as a plug-in.
While the plot symbol and color can be changed by clicking on the plot legend, users generally interact with the tool largely through menu-driven control panels, which provide control over the plot appearance and attributes, such as plot labels, plotting ranges, plot symbol and so on. Two of these menu-driven features are of special interest: (1) control of the plot type: linear, logarithmic, or histogram; (2) enable overplotting of additional data, such as additional spectra or light curves.
Broadly speaking, QtPlot supports two formats: column delimited ASCII tables (IPAC table format), and XML. The IPAC table format is used throughout IRSA to return ASCII data to users and to allow users to upload data files to cross-compare them with IRSA's catalogs. Consequently, QtPlot naturally supports this format.
Of wider interest is XML support. QtPlot utilizes the XDF, which supports transport of multiple n-dimensional tables and file attributes through references in the XML specification. The following is an example of the XML file that describes the display of the brown dwarf 2MASSI J0028394+150141 from Dr. Davy Kirkpatrick's Archive of L Dwarfs.
<?xml version="1.0" encoding="ISO-8859-1" standalone="yes"?> <PlotSet> <XYPlot name="2MASSI J0028394+150141"> <axes> <title> 2MASSI J0028394+150141 (L4.5 V) </title> <xaxis> <scaling> linear </scaling> <min> 6300 </min> <max> 10200 </max> <label> Wavelength (Angstroms) </label> </xaxis> <yaxis> <scaling> linear </scaling> <min> -0.1 </min> <max> 4.5 </max> <label> Normalized Flux F_lambda (ergs/cm^2) s A) </label> </yaxis> </axes> <pointset name="spectrum"> <source> <type> XDF </type> <table> 0028p1501_ascii </table> <xcolumn> wave </xcolumn> <ycolumn> flux </ycolumn> </source> <points> <color> black </color> <symbol> none </symbol> <size> 1% </size> </points> <lines> <color> black </color> <style> solid </style> </lines> </pointset> </XYPlot> <XDF name="0028p1501\underline{ }ascii"> <array name="data table"> <axis axisId="columns" axisDatatype="real"> <axisUnits><unitless/></axisUnits> <valueList size="2"/> </axis> <fieldAxis axisId="rows"> <field name="wave" > <units><unit>Angstroms</unit></units> <dataFormat> <fixed width="17" precision="11"/> </dataFormat> </field> <field name="flux" > <units><unit>ergs/cm^2) s A</unit></units> <dataFormat> <fixed width="11" precision="8"> </dataFormat> </field> </fieldAxis> <data><![CDATA[ 6361.90087890625 0.27137709 .... 10158.09863281250 1.38749599 ]]></data> </array> </XDF> </PlotSet>