overline(xx, y, text), where xx is a 2-vector and y a scalar, draws a horizontal line just above (XX₀, y) to (XX₁, y) and places the given text over it.
overline(xx, yy, text), where both xx and yy are 2-vectors, draws the line just above the larger yy value and extends a vertical line down to the smaller yy value.
The whole thing is displaced by a distance
overlinedist from the data, and the text placement uses the absolute value of
textdist.
If
overlinemin is non-zero, a vertical line is drawn on both ends.
The text argument may be omitted.
Optional arguments datadist, textdist, and minlen override global settings.