title: Plot data points with connecting lines but which leave gaps
body: <p>I like following <code>linespoints</code> plotting style:<br>
  <a href="http://www.gnuplotting.org/join-data-points-with-non-continuous-lines/" rel="nofollow noreferrer">http://www.gnuplotting.org/join-data-points-with-non-continuous-lines/</a></p>
  
  <p>However, I have encountered an issue when I plot several lines with this style:</p>
  
  <p><img src="https://i.stack.imgur.com/RqTHc.png" alt="plot of data points with non-touching lines"></p>
  
  <p>As you can see the second series of points blank-out also the first series (lines and points), what I don't want to happen.</p>
  
  <p>Feature of gnuplot which makes this possible is <code>pointinterval</code> and <code>pointintervalbox</code>.</p>
  
  <p>Documentation of gnuplot:</p>
  
  <blockquote>
    <p>A negative value of <code>pointinterval</code>, e.g. -N, means that point symbols
    are drawn only for every Nth point, and that a box (actually circle)
    behind each point symbol is blanked out by filling with the <strong>background
    color</strong>. The command <code>set pointintervalbox</code> controls the radius of this
    blanked-out region. It is a multiplier for the default radius, which
    is equal to the point size.</p>
  </blockquote>
  
  <p><a href="http://www.bersch.net/gnuplot-doc/set-show.html#set-pointintervalbox" rel="nofollow noreferrer">http://www.bersch.net/gnuplot-doc/set-show.html#set-pointintervalbox</a> </p>
  
  <p>Since the doc says, fill with background color I was hoping using a <strong>transparent</strong> background the issue could be resolved, but it seems to be that the color white is used.</p>
  
  <h3>Gnuplot version</h3>
  
  <pre><code>gnuplot&gt; show version long
  
      G N U P L O T
      Version 5.0 patchlevel 0    last modified 2015-01-01 
  
      Copyright (C) 1986-1993, 1998, 2004, 2007-2015
      Thomas Williams, Colin Kelley and many others
  
      gnuplot home:     http://www.gnuplot.info
      faq, bugs, etc:   type "help FAQ"
      immediate help:   type "help"  (plot window: hit 'h')
  Compile options:
  -READLINE  +LIBREADLINE  +HISTORY  
  -BACKWARDS_COMPATIBILITY  +BINARY_DATA  
  +GD_PNG  +GD_JPEG  +GD_TTF  +GD_GIF  +ANIMATION  
  -USE_CWDRC  +HIDDEN3D_QUADTREE  
  +DATASTRINGS  +HISTOGRAMS  +OBJECTS  +STRINGVARS  +MACROS  +THIN_SPLINES  +IMAGE  +USER_LINETYPES +STATS +EXTERNAL_FUNCTIONS 
  </code></pre>
  
  <h3>Minimal Working Example (MWE):</h3>
  
  <p><code>gnuplot-space-line-mark-style.gp</code></p>
  
  <pre><code>reset
  set terminal pngcairo transparent size 350,262 enhanced font 'Verdana,10'
  show version
  set output 'non-continuous_lines.png'
  set border linewidth 1.5
  set style line 1 lc rgb '#0060ad' lt 1 lw 2 pt 7 pi -1 ps 1.5
  set style line 2 lc rgb '#0020ad' lt 1 lw 2 pt 7 pi -1 ps 1.5
  set pointintervalbox 3
  unset key
  set ytics 1
  set tics scale 0.75
  set xrange [0:5]
  set yrange [0:4]
  plot 'plotting_data1.dat' with linespoints ls 1,\
       'plotting_data2.dat' with linespoints ls 2
  </code></pre>
  
  <p><code>plotting_data1.dat</code></p>
  
  <pre><code># X   Y
    1   2
    2   3
    3   2
    4   1
  </code></pre>
  
  <p><code>plotting_data2.dat</code></p>
  
  <pre><code># X   Y
    1.2   2.4
    2   3.5
    3   2.5
    4   1.2
  </code></pre>
  
  <h3>UPDATE</h3>
  
  <p>A working <a href="http://pgfplots.sourceforge.net/" rel="nofollow noreferrer"><code>pgfplots</code></a> solution is given on <a href="https://tex.stackexchange.com/a/194442/8917">tex.stackoverflow.com</a></p>
  
  <p><img src="https://i.stack.imgur.com/FJQLZ.png" alt="enter image description here"></p>