class_docstr: Calculate the interquartile range of a column.
  
  :param column_name:
      The name of a column containing :class:`.Number` data.
code: def __init__(self, column_name):
      self._column_name = column_name
      self._percentiles = Percentiles(column_name)
  
file_path: agate/agate/aggregations/iqr.py
imports: from agate.aggregations.base import Aggregation
  from agate.aggregations.has_nulls import HasNulls
  from agate.aggregations.percentiles import Percentiles
  from agate.data_types import Number
  from agate.exceptions import DataTypeError
  from agate.warns import warn_null_calculation
label_desc: Use image node_id 1 to create a new IQR object from inherited base classes: Aggregation with example: obj = IQR(column_name)