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The XYCorr () form
plots an error ellipse (or rectangle or other similar figure)
defined by errors in the X and Y directions,
and a correlation between the two errors.
The supplied correlation is a dimensionless value in the range 1..+1
and is equal to the covariance divided by the product
of the X and Y errors. The covariance matrix is thus:
[ xerr*xerr xerr*yerr*xycorr ]
[ xerr*yerr*xycorr yerr*yerr ]
This plot type is suitable for use with the
<x>_error
and
<x>_<y>_corr
columns in the Gaia source catalogue.
Example XYCorr plot
XYCorr form configuration panel
The configuration options are:

Shading Mode
 See Appendix A.4.6.

X/Y Error
 The error along the horizontal and vertical directions,
as column names or expressions.

XY Correlation
 Correlation beteween the errors in the horizontal and vertical
directions.
This is a dimensionless quantity in the range 1..+1,
and is equivalent to the covariance divided by the product
of the X and Y error values themselves.
It corresponds to the
x_y_corr
values
supplied in the Gaia source catalogue.

Ellipse
 Ellipse graphical representation, selected from a range of options
(includes also rectangles, crosses etc).
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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:
topcatuser@jiscmail.ac.uk