Previous: Text String Format, Up: Fonts and Markers
The GNU libplot
library supports a standard set of marker
symbols, numbered 0...31. A marker symbol is a visual
representation of a point. The libplot
marker symbols are the
symbols that the graph
program will plot at each point of a
dataset, if the ‘-S’ option is specified.
Like a text string, a marker symbol has a font size. In any output format, a marker symbol is guaranteed to be visible if its font size is sufficiently large. Marker symbol #0 is an exception to this: by convention, symbol #0 means no symbol at all. Marker symbols in the range 1...31 are defined as follows.
The interpretation of marker symbols 1 through 5 is the same as in the well known Graphical Kernel System (GKS).
By convention, symbols 32 and up are interpreted as characters in a
certain text font. For libplot
, this is simply the current font.
But for the graph
program, it is the symbol font selected
with the ‘--symbol-font-name’ option. By default, the symbol
font is the ZapfDingbats font except in graph -T png
, graph
-T pnm
, graph -T gif
, graph -T pcl
, graph -T hpgl
and graph -T tek
. Those variants of graph
normally have
no access to ZapfDingbats and other Postscript fonts, so they use the
HersheySerif font instead.
Many of the characters in the ZapfDingbats font are suitable for use as marker symbols. For example, character #74 is the Texas star. Doing
echo 0 0 1 2 2 1 3 2 4 0 | graph -T ps -m 0 -S 74 0.1 > plot.ps
will produce a Postscript plot consisting of five data points, not joined by line segments. Each data point will be marked by a Texas star, of a large font size (0.1 times the width of the plotting box).
If you are using graph -T pcl
or graph -T hpgl
and wish to
use font characters as marker symbols, you should consider using the
Wingdings font, which is available when producing PCL 5 or HP-GL/2
output. Doing
echo 0 0 1 2 2 1 3 2 4 0 | graph -T pcl -m 0 --symbol-font Wingdings -S 181 0.1 > plot.pcl
will produce a PCL 5 plot that is similar to the preceding Postscript plot. The Wingdings font has the Texas star in location #181.