title: usecols in loadtxt
body: <p>I founds this error in multiple question but it is not fixed or explained
  Ex. <a href="https://stackoverflow.com/questions/11742156/reading-in-single-str-column-with-loadtxt">Reading in single str column with loadtxt</a></p>
  
  <p>I have a problem with the following line (<code>import numpy as np</code>)</p>
  
  <pre><code>    symbols = np.loadtxt('filename.csv',
                 dtype={'names': ('ticker', 'year', 'month','day'),
                        'formats': ('S10','i4','i2','i2')},
                  delimiter=',',skiprows=1, usecols=(0,))
  </code></pre>
  
  <p>with following data </p>
  
  <pre><code>ticker  year    month   day
  GPD.TO  2010    8   16
  HAO.V   2010    8   16
  RDS.V   2010    8   16
  MD.V    2010    8   16
  </code></pre>
  
  <p>It gives me a</p>
  
  <pre><code>IndexError: list index out of range
  </code></pre>
  
  <p>When I run that line without <code>usecols</code> it works fine and returns all 4 columns fine.</p>
  
  <p>I looked at many other questions on google and Stackoverflow but this isnt answered</p>