special linetypes

Two special numerical linetypes are worth mentioning. These cannot be modified by "set linetype".

Linetype 0 is a terminal-dependent linetype used by the program as the default for axis lines (see "zeroaxis"). It is always a dotted line if the terminal supports this. For terminals that do not support a separate dashtype property this may be the only way to get a dotted line.

Linetype -1 is the basic linetype. It corresponds to a solid line with width 1.0 in foreground color (normally black). The program uses this as the default for many plot elements (plot borders, label text, arrows).

The program also recognizes a few non-numerical linetypes.

lt black specifies a solid black line.

lt background or lt bgnd specifies a solid line with the background color of the current terminal. See background.

lt nodraw skips drawing the line altogether. This is useful in conjunction with plot style linespoints. It allows you to suppress the line component of the plot while retaining point properties that are available only in this plot style. For example

     plot f(x) with linespoints lt nodraw pointinterval -3

will draw only every third point and will isolate it by placing a small circle of background color underneath it. See linespoints. lt nodraw may also be used to suppress a particular set of lines that would otherwise be drawn automatically. For example you could suppress certain contour levels in a contour plot by setting their linetype to nodraw.