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#### A.4.5.37 XYErrors Form

The XYErrors form (), available from the XYArray Layer Control, draws a set of error bars representing all the elements of X, Y array-valued coordinates, resulting in a sequence of error bars for each table row. Symmetric or asymmetric vertical and/or horizontal error bars may be drawn, and the shape of the error "bars" is quite configurable, including error ellipses, rectangles etc.

Example XYErrors plot

XYErrors form configuration panel

The configuration options are:

Shading Mode
  See Appendix A.4.6.
X Positive Errors
X Negative Errors
Y Positive Errors
Y Negative Errors
  Array values giving error extents in X and Y directions corresponding to the plotted data position arrays. For each axis, if both positive and negative values are filled in, the errors will be asymmetric. If the negative value is blank (either because the coordinate is not filled in, or because its value is NaN for that row), the error bars will be symmetric, i.e. the negative error bar will be the same size as the positive one. If you want to ensure only a positive error bar is plotted, supply zero for the corresponding negative errors. Either X, Y or both error values may be supplied.

  The column names or expressions used here must be array values, matching the length of the data array values. If you need to create or manipulate array values, the functions in the Arrays class may be of use here.

Error Bar
  Error bar shape from a list of options.
Thickness
  Controls the line thickness used when drawing error bars. Zero, the default value, means a 1-pixel-wide line is used. Larger values make drawn lines thicker, but note changing this value will not affect all shapes, for instance filled rectangles contain no line drawings.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk