title: Find unique elements of floating point array in numpy (with comparison using a delta value)
body: <p>I've got a <code>ndarray</code> of floating point values in numpy and I want to find the unique values of this array. Of course, this has problems because of floating point accuracy...so I want to be able to set a delta value to use for the comparisons when working out which elements are unique.</p>
  
  <p>Is there a way to do this? At the moment I am simply doing:</p>
  
  <pre><code>unique(array)
  </code></pre>
  
  <p>Which gives me something like:</p>
  
  <pre><code>array([       -Inf,  0.62962963,  0.62962963,  0.62962963,  0.62962963,
      0.62962963])
  </code></pre>
  
  <p>where the values that look the same (to the number of decimal places being displayed) are obviously slightly different.</p>