Merge pull request #554 from RocketPy-Team/enh/function-remove-outliers

ENH: adds `Function.remove_outliers` method

CHANGELOG.md

@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Added
 
+- ENH: adds `Function.remove_outliers` method [#554](https://github.com/RocketPy-Team/RocketPy/pull/554)
 
 ### Changed
 - ENH: Optional argument to show the plot in Function.compare_plots [#563](https://github.com/RocketPy-Team/RocketPy/pull/563)

rocketpy/mathutils/function.py

@@ -1144,6 +1144,51 @@ def low_pass_filter(self, alpha, file_path=None):
             title=self.title,
         )
 
+    def remove_outliers_iqr(self, threshold=1.5):
+        """Remove outliers from the Function source using the interquartile
+        range method. The Function should have an array-like source.
+
+        Parameters
+        ----------
+        threshold : float, optional
+            Threshold for the interquartile range method. Default is 1.5.
+
+        Returns
+        -------
+        Function
+            The Function with the outliers removed.
+
+        References
+        ----------
+        [1] https://en.wikipedia.org/wiki/Outlier#Tukey's_fences
+        """
+
+        if callable(self.source):
+            raise TypeError(
+                "Cannot remove outliers if the source is a callable object."
+                + " The Function.source should be array-like."
+            )
+
+        x = self.x_array
+        y = self.y_array
+        y_q1 = np.percentile(y, 25)
+        y_q3 = np.percentile(y, 75)
+        y_iqr = y_q3 - y_q1
+        y_lower = y_q1 - threshold * y_iqr
+        y_upper = y_q3 + threshold * y_iqr
+
+        y_filtered = y[(y >= y_lower) & (y <= y_upper)]
+        x_filtered = x[(y >= y_lower) & (y <= y_upper)]
+
+        return Function(
+            source=np.column_stack((x_filtered, y_filtered)),
+            inputs=self.__inputs__,
+            outputs=self.__outputs__,
+            interpolation=self.__interpolation__,
+            extrapolation=self.__extrapolation__,
+            title=self.title,
+        )
+
     # Define all presentation methods
     def __call__(self, *args):
         """Plot the Function if no argument is given. If an

tests/unit/test_function.py

@@ -276,3 +276,33 @@ def test_set_discrete_based_on_model_non_mutator(linear_func):
     assert isinstance(func, Function)
     assert discretized_func.source.shape == (4, 2)
     assert callable(func.source)
+
+
+@pytest.mark.parametrize(
+    "x, y, expected_x, expected_y",
+    [
+        (
+            np.array([1, 2, 3, 4, 5, 6]),
+            np.array([10, 20, 30, 40, 50000, 60]),
+            np.array([1, 2, 3, 4, 6]),
+            np.array([10, 20, 30, 40, 60]),
+        ),
+    ],
+)
+def test_remove_outliers_iqr(x, y, expected_x, expected_y):
+    """Test the function remove_outliers_iqr which is expected to remove
+    outliers from the data based on the Interquartile Range (IQR) method.
+    """
+    func = Function(source=np.column_stack((x, y)))
+    filtered_func = func.remove_outliers_iqr(threshold=1.5)
+
+    # Check if the outliers are removed
+    assert np.array_equal(filtered_func.x_array, expected_x)
+    assert np.array_equal(filtered_func.y_array, expected_y)
+
+    # Check if the other attributes are preserved
+    assert filtered_func.__inputs__ == func.__inputs__
+    assert filtered_func.__outputs__ == func.__outputs__
+    assert filtered_func.__interpolation__ == func.__interpolation__
+    assert filtered_func.__extrapolation__ == func.__extrapolation__
+    assert filtered_func.title == func.title