title: slicing data in pandas
body: <p>This is likely a really simple question, but it's one I've been confused about and stuck on for a while, so I'm hoping I might get some help. </p>
  
  <p>I'm using cross validation to test my data set, but I'm finding that indexing the pandas df is not working as I'm expecting. Specifically, when I print out x_test, I find that there are no data points for x_test. In fact, there are indexes but no columns. </p>
  
  <pre><code>k = 10
  N = len(df)
  n = N/k + 1
  for i in range(k):
      print i*n, i*n+n
      x_train = df.iloc[i*n: i*n+n]
      y_train = df.iloc[i*n: i*n+n]
      x_test = df.iloc[0:i*n, i*n+n:-1]
      print x_test
  </code></pre>
  
  <p>Typical output: </p>
  
  <pre><code>0 751
  Empty DataFrame
  Columns: []
  Index: []
  751 1502
  Empty DataFrame
  Columns: []
  Index: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, ...]
  </code></pre>
  
  <p>I'm trying to work out how to get the data to show up. Any thoughts?</p>