title: GNUPLOT: how to only print selected row?
body: <p>I'm using GNUPLOT with a PC.  Is there a way to only plot some selected rows from a data file instead of every rows?
  for example I have the following data file:
  <br><br><b>   80000.00       1000.000       234.4000<br>
     10000.00       2000.000       237.2000<br>
     20000.00       3000.000       240.0000<br>
     30000.00       4000.000       242.8000<br>
     40000.00       5000.000       245.3000<br>
     10000.00       1000.000       247.4000<br>
     20000.00       2000.000       249.7000<br>
     30000.00       3000.000       252.8000<br>
     10000.00       1000.000       257.7000<br>
     20000.00       2000.00        263.4000<br>
     30000.00       3000.00        269.6000<br>
     10000.00       1000.00        275.8000<br>
     20000.00       2000.00        280.3000<br>
     30000.00       3000.00        286.7000    </b><br><br>
  What if I only want to plot all the second column with value "1000"?  Any tricks to do this?  Thank you very much in advance.</p>