title: Plotting block data in 3d using different colors and smoothing the lines in Gnuplot or Octave
body: <p>I am trying to plot (with Gnuplot) some basic 3d data from one file which is pretty much like that:</p>
  
  <pre><code>N     M    t1      t2       t3       t4
  1000 1000 0.05268 0.04711 0.003947 0.003348
  1000 2000 0.05743 0.04214 0.007577 0.006486
  1000 3000 0.08465 0.04193 0.011329 0.009654
  
  
  2000 1000 0.10726 0.08845 0.013593 0.012397
  2000 2000 0.21065 0.10817 0.026525 0.024390
  2000 3000 0.31528 0.16960 0.039772 0.036405
  
  
  3000 1000 0.25415 0.14845 0.031082 0.026364
  3000 2000 0.47345 0.25227 0.060887 0.051840
  3000 3000 0.70612 0.36866 0.091311 0.077432
  </code></pre>
  
  <p>The idea is to plot it in some way I could see t1,t2,t3 and t4 for each N and M. It may be a lot of data to plot in only one graph, I know that. First of all, I have started with t1 plotting this way:</p>
  
  <pre><code>splot 'aux' u 1:2:3 w lp
  </code></pre>
  
  <p>and I get something like that<img src="https://i.stack.imgur.com/zWIx8.jpg" alt="enter image description here"></p>
  
  <p>I would like to smooth a bit those lines and give them a different color. Is there any way to do something for it? Also any ideas to improve it in any other way would be very nice.</p>