class_docstr: Divide a column into 100 equal-size groups using the "CDF" method.
  
  See `this explanation <http://www.amstat.org/publications/jse/v14n3/langford.html>`_
  of the various methods for computing percentiles.
  
  "Zeroth" (min value) and "Hundredth" (max value) percentiles are included
  for reference and intuitive indexing.
  
  A reference implementation was provided by
  `pycalcstats <https://code.google.com/p/pycalcstats/>`_.
  
  This aggregation can not be applied to a :class:`.TableSet`.
  
  :param column_name:
      The name of a column containing :class:`.Number` data.
docstr: :returns:
      An instance of :class:`Quantiles`.
code: def run(self, table):
      """
      :returns:
          An instance of :class:`Quantiles`.
      """
      column = table.columns[self._column_name]
  
      data = column.values_without_nulls_sorted()
  
      if not data:
          return Quantiles([None for percentile in range(101)])
  
      # Zeroth percentile is first datum
      quantiles = [data[0]]
  
      for percentile in range(1, 100):
          k = len(data) * (float(percentile) / 100)
  
          low = max(1, int(math.ceil(k)))
          high = min(len(data), int(math.floor(k + 1)))
  
          # No remainder
          if low == high:
              value = data[low - 1]
          # Remainder
          else:
              value = (data[low - 1] + data[high - 1]) / 2
  
          quantiles.append(value)
  
      # Hundredth percentile is final datum
      quantiles.append(data[-1])
  
      return Quantiles(quantiles)
  
file_path: agate/agate/aggregations/percentiles.py
imports: import math
  from agate.aggregations.base import Aggregation
  from agate.aggregations.has_nulls import HasNulls
  from agate.data_types import Number
  from agate.exceptions import DataTypeError
  from agate.utils import Quantiles
  from agate.warns import warn_null_calculation
label_desc: Use image node_id 3 for calling the Percentiles obj's underlying member method code with example usage: obj.run(table) and returns: Quantiles, Quantiles