title: Numpy histogram of large arrays
body: <p>I have a bunch of csv datasets, about 10Gb in size each. I'd like to generate histograms from their columns. But it seems like the only way to do this in numpy is to first load the entire column into a numpy array and then call <code>numpy.histogram</code> on that array. This consumes an unnecessary amount of memory.</p>
  
  <p>Does numpy support online binning? I'm hoping for something that iterates over my csv line by line and bins values as it reads them. This way at most one line is in memory at any one time.</p>
  
  <p>Wouldn't be hard to roll my own, but wondering if someone already invented this wheel.</p>