title: Python bob package API - how to format input data
body: <p>I'm trying to use the bob package which is installed on my ubuntu using the Conda; however while using any of the measurement APIs like the <code>bob.measure.eer_threshold</code> the following error appears. I've prepared the data in 1D array but the error still exists. I've also tried to pass the pure 1D array to the function but it doesn't work.  The error:</p>
  
  <pre><code>Traceback (most recent call last):   File "Test_bob.py", line 29, in &lt;module&gt;
  threshold = bob.measure.eer_threshold(negatives, positives) ValueError: cannot convert `numpy.ndarray' which doesn't behave (memory contiguous, aligned, C-style, minimum 1 and up to 4 dimensions) into a `bob.blitz.array'
  </code></pre>
  
  <p>This is the code:</p>
  
  <pre><code>import bob
  import bob.measure
  import bob.blitz
  import math
  import numpy
  from matplotlib import pyplot
  
  fImpostor= open("Impostor.txt", "r")
  fGenuine= open("Genuine.txt", "r")
  
  positive_scores = []
  negative_scores = []
  
  for line in fImpostor:
      ImpScore = line.split()
      negative_scores.append(ImpScore[0])
  fImpostor.close()
  
  for line in fGenuine:
      GenScore = line.split()
      positive_scores.append(GenScore[0])
  fGenuine.close()
  
  positives = numpy.array(positive_scores)
  negatives = numpy.array(negative_scores)
  
  threshold = bob.measure.eer_threshold(negatives, positives)
  FAR, FRR = bob.measure.eer_rocch(negatives, positives)
  </code></pre>
  
  <p>And this is the <code>Genuine.txt</code> file:</p>
  
  <pre><code>8873
  2601
  2554
  11872
  3867
  4048
  6983
  3833
  3988
  5321
  2761
  2139
  8498
  2719
  3128
  3790
  2937
  2394
  </code></pre>
  
  <p>and the <code>Impostor.txt</code>:</p>
  
  <pre><code>2941
  3486
  4051
  3416
  2176
  2222
  1758
  1856
  2283
  3491
  3248
  3159
  4027
  1300
  2102
  1437
  1420
  1776
  4025
  3888
  2522
  3557
  </code></pre>
  
  <p>please help me how to format and prepare data for such bob API methods.</p>