CONNECT(sx,sy{,sz},ex,ey{,ez}); Draw line from (sx,sy{,sz}) to (ex,ey{,ez})

The CONNECT procedure will draw a connecting line between two specified
points in the plot area.  The two points are (sx,sy) and (ex,ey) where
'sx', 'sy', 'ex', and 'ey' are expressions specifying values with
respect to the current plot scaling.  Thus plot scaling values YMIN,
YMAX, etc.  must be set before the CONNECT statement is executed.  If
any of the parameters contains a variable, an implicit loop will be
performed and multiple line segments will be drawn, one for each step
time.

CONNECT will accept optional Z axis coordinates; in which case the 3D
plot mode is enabled for subsequent plots until an ERASE is performed.
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Use this procedure for connecting embedded text labels to points on a
graph, drawing boxes to contain text labels, drawing error bars,
showing the difference between two values, or drawing parametrically
generated traces.

Line segments output via CONNECT are not given trace numbers and,
unless a color is specified via a COLOR statement, will appear in
yellow (on graphics interfaces that support color).
