title: How do I plot three columns of data (x, y, dependent_variable)?
body: <p>I have three columns of data in a .dat file . The first column is the x coordinate value, the second column is the y coordinate value, and the third column is the data point, which is dependent on both the x and y coordinates.
  I want to plot every value of the third column of data versus every value of the first two columns (x and y coordinates of the same "line") giving a curve for every combination(each .dat line) in order to have N (number of combinations) curves in the same diagramm.
  For example..lets plot data of line 1 with x,y of line 1 -->  curve 1 the same for curve 2 curve 3 etc...all these curves in the same diagramm</p>
  
  <p>this is the .dat file format (x,y,data)</p>
  
  <pre><code>                                 .dat file
           x                          y                         data
    0.0000000000000000        0.0000000000000000        1.0000000000000000     
    6.66666666666666657E-002   0.0000000000000000       0.99925295784900281     
    0.13333333333333333        0.0000000000000000       0.99717167897454517     
    0.20000000000000001        0.0000000000000000       0.99416622424560275     
    0.26666666666666666        0.0000000000000000       0.99070882825542761     
    0.33333333333333331        0.0000000000000000       0.98719255818610696     
    0.40000000000000002        0.0000000000000000       0.98387860924473813     
    0.46666666666666667        0.0000000000000000       0.98090550759659945     
    0.53333333333333333        0.0000000000000000       0.97832263784606033     
    0.59999999999999998        0.0000000000000000       0.97612458355657861     
    0.66666666666666663        0.0000000000000000       0.97427724465100551     
    0.73333333333333328        0.0000000000000000       0.97273477472974534     
    0.80000000000000004        0.0000000000000000       0.97144934783540904     
    0.86666666666666670        0.0000000000000000       0.97037616025481399   
  
  </code></pre>
  
  <p>i think this job needs a script for gnuplot but im new at gnuplot so i dont know how to do it</p>
  
  <p>the wanted outcome must be , many plotting lines for every combination (each .dat line) x,y,datain one diagramm</p>