As of Version 2.0 (October 2008), STILTS offers table plotting commands. These acquire a data point from each line of one or more input tables, perhaps influenced by the pipelining operations described in Section 6, and generate some kind of graphical plot from the result. At time of writing, the following plot types are available:
tcubefor generating N-dimensional histograms as FITS files. It is hoped to add more plot types in future releases.
The plotting commands offer considerable control over what is plotted and how it is represented, and thus unavoidably have rather a large number of parameters. When looking at the command documentation in Appendix B the Usage sections may look rather daunting. However, the discussion below and the Examples sections should help. Generating a simple plot is straightforward and can be done with only three or four parameters; if you have more complicated requirements for data selection or specific preferences for appearance then you can consult the documentation for the additional options.
As a simple example, if a file "cat.fits" contains the columns RMAG and BMAG for red and blue magnitudes, you can draw a two-dimensional colour-magnitude scatter plot with the command:
stilts plot2d in=cat.fits xdata=RMAG ydata=BMAG-RMAGSince an output file is not specified, the plot is shown on the screen for convenience. To send the output to a PNG file, do instead:
stilts plot2d in=cat.fits xdata=RMAG ydata=BMAG out=plot.png ofmt=pngin some cases (including the above), the
ofmtparameter is not required since STILTS may be able to guess the format from the output file name. Various other options for output and graphics formats are described in Section 8.2 and Section 8.3
Some of the parameters use suffixes to define data sets and therefore behave a bit differently from the parameters elsewhere in STILTS - a discussion of these is given in the following subsection. Some other plotting-specific topics are also discussed below.