Add diff for FloatColumn (#300)

* Add tests

* Add precision to diff

* Add specificity to diff parent method call

* Simplified test

dataprofiler/profilers/float_column_profile.py

@@ -3,6 +3,7 @@
 import math
 import numpy as np
 
+from . import utils
 from .numerical_column_stats import NumericStatsMixin
 from .base_column_profilers import BaseColumnProfiler, \
     BaseColumnPrimitiveTypeProfiler
@@ -105,6 +106,25 @@ def __add__(self, other):
 
         return merged_profile
 
+    def diff(self, other_profile, options=None):
+        """
+        Finds the differences for FloatColumnss.
+
+        :param other_profile: profile to find the difference with
+        :type other_profile: FloatColumn
+        :return: the FloatColumn differences
+        :rtype: dict
+        """
+        differences = NumericStatsMixin.diff(self, other_profile, options=None)
+        other_precision = other_profile.profile['precision']
+        precision_diff = dict()
+        for key in self.profile['precision'].keys():
+            precision_diff[key] = utils.find_diff_of_numbers(
+                self.profile['precision'][key], other_precision[key])
+        precision_diff.pop("confidence_level")
+        differences["precision"] = precision_diff
+        return differences
+
     @property
     def profile(self):
         """

dataprofiler/tests/profilers/test_float_column_profile.py

@@ -1299,3 +1299,45 @@ def test_insufficient_counts(self):
             # to make sure NO warnings were thrown since we have
             # a sufficient match count.
             self.assertEqual(0, len(w))
+
+    def test_diff(self):
+        data = [2.5, 12.5, 'not a float', 5, 'not a float']
+        df = pd.Series(data).apply(str)
+        profiler1 = FloatColumn(df.name)
+        profiler1.update(df)
+        profile1 = profiler1.profile
+
+        data = [1, 15, 0.5, 0]
+        df = pd.Series(data).apply(str)
+        profiler2 = FloatColumn(df.name)
+        profiler2.update(df)
+        profile2 = profiler2.profile
+
+        # Assert the difference report is correct
+        diff = profiler1.diff(profiler2)
+        expected_diff = {
+            'max': -2.5,
+            'mean': profile1['mean'] - profile2['mean'],
+            'min': 2.5,
+            'stddev': profile1['stddev'] - profile2['stddev'],
+            'sum': 3.5,
+            'variance': profile1['variance'] - profile2['variance'],
+            'precision': {
+                'min': 1,
+                'max': 1,
+                'mean': 1,
+                'var': profile1['precision']['var'] - profile2['precision']['var'],
+                'std': profile1['precision']['std'] - profile2['precision']['std'],
+                'sample_size': -1,
+                'margin_of_error':
+                    profile1['precision']['margin_of_error'] - profiler2['precision']['margin_of_error']
+            }
+        }
+        self.assertDictEqual(expected_diff, diff)
+
+        # Assert type error is properly called
+        with self.assertRaises(TypeError) as exc:
+            profiler1.diff("Inproper input")
+        self.assertEqual(str(exc.exception),
+                         "Unsupported operand type(s) for diff: 'FloatColumn' and"
+                         " 'str'")