title: Unexpected behaviour of 'every' gnuplot keyword inside 'do for' loop
body: <p>Unexpected behaviour of <code>'every'</code> inside <code>'do for'</code> loop compared to its behaviour outside the loop</p>
  
  <pre><code>set style line 1 linecolor rgb "blue" pointtype 7 pointsize 3 lt 1
  #plot 4 points
  plot 'every_test.txt' every 1:1:0:0:3:0 u 1:2 with points linestyle 1 
  # Next 4 lines, when active, draw 2 arrows from 2nd point to 1st &amp; 3rd 
  #pause 1
  #replot '' every 1:1:1:0:1:0 u 3:4:5:6 with vectors filled head linestyle 1
  #pause 1
  #replot '' every 1:1:2:0:2:0 u 3:4:5:6 with vectors filled head linestyle 1
  # Try 'do for' loop instead of preceding 4 line to draw the 2 arrows
  do for [k = 1:2] {
     pause 1
     replot '' every 1:1:k:0:k:0 u 3:4:5:6 with vectors filled head linestyle 1
  }
  # Loop behaves unexpectedly. 
  # It draws 1st arrow, removes it [how does replot even do that!] 
  # then draws 2nd arrow. Final result is 2nd arrow only. 
  replot '' every 1:1:1:0:1:0 u 3:4:5:6 with vectors filled head linestyle 1
  # Line above attempts to restore 1st arrow, but only results in error:
  # "undefined variable: k" even though it makes no reference to k.
  </code></pre>
  
  <p>Data in 'every_test.txt:</p>
  
  <pre><code>1  2 
  2  3 1.9  2.9 -0.8 -0.8
  3  2 2.1  2.9  0.8 -0.8
  4  1
  
  5  3
  6  4
  </code></pre>