Add number of datapoints check

Author: MDUYN

pyindicators/__init__.py

@@ -4,6 +4,7 @@
     is_below, is_above, get_slope, has_any_higher_then_threshold, \
     has_slope_above_threshold, has_any_lower_then_threshold, \
     has_values_above_threshold, has_values_below_threshold
+from .exceptions import PyIndicatorException
 
 __all__ = [
     'sma',
@@ -30,4 +31,5 @@
     'has_any_lower_then_threshold',
     'has_values_above_threshold',
     'has_values_below_threshold',
+    'PyIndicatorException',
 ]

pyindicators/indicators/crossover.py

@@ -35,6 +35,13 @@ def crossover(
 
     # Restrict data to the last `data_points` rows if specified
     if number_of_data_points is not None:
+
+        if number_of_data_points < 2:
+            raise PyIndicatorException(
+                "The number of data points must be greater or equal than 2 for"
+                " crossover detection."
+            )
+
         data = data.tail(number_of_data_points) \
             if isinstance(data, PdDataFrame) \
             else data.slice(-number_of_data_points)
@@ -100,6 +107,14 @@ def is_crossover(
     if len(data) < 2:
         return False
 
+    if number_of_data_points is None:
+        number_of_data_points = len(data)
+    elif number_of_data_points < 2:
+        raise PyIndicatorException(
+            "The number of data points must be greater or equal than 2 for"
+            " crossover detection."
+        )
+
     if crossover_column is None:
         crossover_column = f"{first_column}_crossover_{second_column}"
         data = crossover(
@@ -111,9 +126,6 @@ def is_crossover(
             strict=strict
         )
 
-    if number_of_data_points is None:
-        number_of_data_points = len(data)
-
     # If crossunder_column is set, check for a value of 1
     # in the last data points
     if isinstance(data, PdDataFrame):

pyindicators/indicators/crossunder.py

@@ -17,6 +17,12 @@ def crossunder(
 
     if number_of_data_points is not None:
 
+        if number_of_data_points < 2:
+            raise PyIndicatorException(
+                "The number of data points must be greater or equal than 2 for"
+                " crossunder detection."
+            )
+
         if isinstance(data, PdDataFrame):
             data = data.tail(number_of_data_points).copy()
         else:
@@ -63,6 +69,14 @@ def is_crossunder(
     if len(data) < 2:
         return False
 
+    if number_of_data_points is None:
+        number_of_data_points = len(data)
+    elif number_of_data_points < 2:
+        raise PyIndicatorException(
+            "The number of data points must be greater or equal than 2 for"
+            " crossover detection."
+        )
+
     if crossunder_column is None:
         crossunder_column = f"{first_column}_crossunder_{second_column}"
         data = crossunder(
@@ -74,9 +88,6 @@ def is_crossunder(
             strict=strict
         )
 
-    if number_of_data_points is None:
-        number_of_data_points = len(data)
-
     if isinstance(data, PdDataFrame):
         return data[crossunder_column].tail(number_of_data_points)\
             .eq(1).any()

tests/indicators/test_crossover.py

@@ -2,7 +2,7 @@
 import polars as pl
 from unittest import TestCase
 
-from pyindicators import is_crossover
+from pyindicators import is_crossover, PyIndicatorException
 
 
 class TestCrossover(TestCase):
@@ -106,3 +106,18 @@ def test_crossover_polars(self):
                 number_of_data_points=3
             )
         )
+
+    def test_throws_exception_when_number_of_data_points_is_less_than_2(self):
+        df = pd.DataFrame({
+            "EMA_50": [200, 201, 202, 203, 204, 205, 206, 208, 208, 210],
+            "EMA_200": [200, 201, 202, 203, 204, 205, 206, 207, 209, 209],
+            "DateTime": pd.date_range("2021-01-01", periods=10, freq="D")
+        })
+
+        # Set index to DateTime
+        df.set_index("DateTime", inplace=True)
+
+        with self.assertRaises(PyIndicatorException):
+            is_crossover(
+                df, first_column="EMA_50", second_column="EMA_200", number_of_data_points=1
+            )

tests/indicators/test_crossunder.py

@@ -2,7 +2,7 @@
 import polars as pl
 from unittest import TestCase
 
-from pyindicators import is_crossunder
+from pyindicators import is_crossunder, PyIndicatorException
 
 
 class TestCrossover(TestCase):
@@ -174,3 +174,18 @@ def test_crossunder_polars(self):
                 strict=False
             )
         )
+
+    def test_throws_exception_when_number_of_data_points_is_less_than_2(self):
+        df = pd.DataFrame({
+            "EMA_50": [200, 201, 202, 203, 204, 205, 206, 208, 208, 210],
+            "EMA_200": [200, 201, 202, 203, 204, 205, 206, 207, 209, 209],
+            "DateTime": pd.date_range("2021-01-01", periods=10, freq="D")
+        })
+
+        # Set index to DateTime
+        df.set_index("DateTime", inplace=True)
+
+        with self.assertRaises(PyIndicatorException):
+            is_crossunder(
+                df, first_column="EMA_50", second_column="EMA_200", number_of_data_points=1
+            )