[gnuplot] Gnuplot line types

Until version 4.6

The dash type of a linestyle is given by the linetype, which does also select the line color unless you explicitely set an other one with linecolor.

However, the support for dashed lines depends on the selected terminal:

1. Some terminals don't support dashed lines, like png (uses libgd)
2. Other terminals, like pngcairo, support dashed lines, but it is disables by default. To enable it, use set termoption dashed, or set terminal pngcairo dashed ....
3. The exact dash patterns differ between terminals. To see the defined linetype, use the test command:

Running

set terminal pngcairo dashed
set output 'test.png'
test
set output

gives:

whereas, the postscript terminal shows different dash patterns:

set terminal postscript eps color colortext
set output 'test.eps'
test
set output

Version 5.0

Starting with version 5.0 the following changes related to linetypes, dash patterns and line colors are introduced:

• A new dashtype parameter was introduced:

  To get the predefined dash patterns, use e.g.

  plot x dashtype 2
  

  You can also specify custom dash patterns like

  plot x dashtype (3,5,10,5),\
       2*x dashtype '.-_'
  

• The terminal options dashed and solid are ignored. By default all lines are solid. To change them to dashed, use e.g.

  set for [i=1:8] linetype i dashtype i
  

• The default set of line colors was changed. You can select between three different color sets with set colorsequence default|podo|classic: