title: Making a graphic of a trained dataset python
body: <pre><code>y1 = []
  y2 = []
  x = []
  for i in range(40):
      #fer dos llistes (error y epoch) y despres fer un plot
      trainer.trainEpochs( 1 )
      trnresult = percentError( trainer.testOnClassData(),trndata['class'] )
      tstresult = percentError( trainer.testOnClassData(dataset=tstdata ),tstdata['class'] )
  
      print "epoch: %4d" % trainer.totalepochs, \
            "  train error: %5.2f%%" % trnresult, \
            "  test error: %5.2f%%" % tstresult
  
      if i==1:
          g=Gnuplot.Gnuplot()
      else:
          y1 = y1.append(float(trnresult))
          y2 = y2.append(float(tstresult))
          x = x.append(i)
  d1=Gnuplot.Data(x,y1,with_="line")
  d2=Gnuplot.Data(x,y2,with_="line")
  g.plot(d1,d2)
  </code></pre>
  
  <p>Hi everyone, first time i post here, but thanks for the work.</p>
  
  <p>Ok, i´m working with neural networks (multi-layer preceptron) and i´m testing with UCI ML repository, i have to make a graphical display of the error versus the number of epochs, but i have no idea what i´m doing wrong, this is the error i got:</p>
  
  <pre><code>y1 = y1.append(float(trnresult))
  AttributeError: 'NoneType' object has no attribute 'append'
  </code></pre>
  
  <p>I´ve tryed with int and float at the y1.append() but i got same errors.
  This is all i get on console:</p>
  
  <pre><code>Number of training patterns:  233
  
  Input and output dimensions:  6 2
  
  First sample (input, target, class):
  
  [ 63.03  22.55  39.61  40.48  98.67  -0.25] [1 0] [ 0.]
  
  Total error: 0.110573541007
  
  epoch:    1   train error: 33.05%   test error: 29.87%
  
  Total error: 0.0953749484982
  
  epoch:    2   train error: 32.19%   test error: 35.06%
  
  Total error: 0.0977600868845
  
  epoch:    3   train error: 27.90%   test error: 29.87%
  
  Traceback (most recent call last):
    File "C:\Python\Practice\dataset.py", line 79, in &lt;module&gt;
      y1 = y1.append(float(trnresult))
  AttributeError: 'NoneType' object has no attribute 'append'
  </code></pre>
  
  <p>Thanks.</p>