2 columns: x y 3 columns: x y major_diam 4 columns: x y major_diam minor_diam 5 columns: x y major_diam minor_diam angle
If only two input columns are present, they are taken as the coordinates of the centers, and the ellipses will be drawn with the default extent (see set style ellipse). The orientation of the ellipse, which is defined as the angle between the major diameter and the plot's x axis, is taken from the default ellipse style (see set style ellipse). If three input columns are provided, the third column is used for both diameters. The orientation angle defaults to zero. If four columns are present, they are interpreted as x, y, major diameter, minor diameter. Note that these are diameters, not radii. An optional 5th column may be used to specify the orientation angle in degrees. The ellipses will also be drawn with their default extent if either of the supplied diameters in the 3-4-5 column form is negative.
In all of the above cases, optional variable color data may be given in an additional last (3th, 4th, 5th or 6th) column. See colorspec for further information.
By default, the major diameter is interpreted in the units of the plot's horizontal axis (x or x2) while the minor diameter in that of the vertical (y or y2). This implies that if the x and y axis scales are not equal, then the major/minor diameter ratio will no longer be correct after rotation. This behavior can be changed with the units keyword, however.
There are three alternatives: if units xy is included in the plot specification, the axes will be scaled as described above. units xx ensures that both diameters are interpreted in units of the x axis, while units yy means that both diameters are interpreted in units of the y axis. In the latter two cases the ellipses will have the correct aspect ratio, even if the plot is resized.
If units is omitted, the default setting will be used, which is equivalent to units xy. This can be redefined by set style ellipse.
Example (draws ellipses, cycling through the available line types):
plot 'data' using 1:2:3:4:(0):0 with ellipses
Copyright 1986 - 1993, 1998, 2004 Thomas Williams, Colin Kelley
Distributed under the gnuplot license (rights to distribute modified versions are withheld).