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### 8.1 Plot Parameters

The plotting commands offer a great deal of control over what is plotted and how it is represented, and thus unavoidably have lots 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 four or five parameters; if you want to represent more complicated data or have 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 plot2plane layer_1=mark in_1=cat.fits x_1=BMAG-RMAG y_1=BMAG

Since an output file is not specified, the plot is shown in a window on the screen. This plot window is "live" - you can resize the window, or pan and zoom around it using the same mouse controls as in TOPCAT. To send the output to a PNG file, do instead:

       stilts plot2plane layer_1=mark in_1=cat.fits x_1=BMAG-RMAG y_1=BMAG out=fig.png

We can adjust the plot by inverting the Y axis so it increases downwards instead of upwards:

       stilts plot2plane
                  yflip=true
                  layer_1=mark in_1=cat.fits x_1=BMAG-RMAG y_1=BMAG

The parameters of the plot now fall into two groups. Global parameters, without suffixes, make global adjustments to the plot. In this example `yflip=true` inverts the Y axis. Layer parameters, with suffixes, are introduced by a `layer` parameter and grouped together by a given suffix. Each layer group defines a plot layer with content to be drawn on the plot surface. In this case the layer is of type `mark` (draw markers) and the suffix is "`_1`". Global and Layer parameters are described separately in the following subsections.

- 8.1.1 Global Parameters
- 8.1.2 Layer Parameters
- 8.1.3 Animation

Next Previous Up Contents
Next: Global Parameters
Up: Plotting
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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk