Remove low values of pressure.

features/ambient.py

@@ -12,6 +12,10 @@ from config.models import (
 )
 from setup import db_engine, session
 
+MINIMUM_PRESSURE_MB = 870
+# The lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes,
+# with a record low of 870 mbar (87 kPa; 26 inHg).
+
 
 def get_ambient_data(usernames: Collection, sensor=None) -> pd.DataFrame:
     """
@@ -57,10 +61,31 @@ def get_ambient_data(usernames: Collection, sensor=None) -> pd.DataFrame:
         )
     else:
         raise KeyError(
-            "Specify one of the ambient sensors: barometer, barometer_sensor, light, temperature, or temperature_sensor."
+            "Specify one of the ambient sensors: "
+            "barometer, barometer_sensor, light, temperature, or temperature_sensor."
         )
 
     query_ambient = query_ambient.filter(Participant.username.in_(usernames))
     with db_engine.connect() as connection:
         df_ambient = pd.read_sql(query_ambient.statement, connection)
     return df_ambient
+
+
+def clean_pressure(df_ambient: pd.DataFrame) -> pd.DataFrame:
+    """
+    Simply removes values lower than MINIMUM_PRESSURE_MB (lowest measured pressure).
+
+    Parameters
+    ----------
+    df_ambient: pd.DataFrame
+        A dataframe of barometer data, which includes measured pressure in double_values_0.
+
+    Returns
+    -------
+    df_ambient: pd.DataFrame
+        The same dataframe with rows with low values of pressure removed.
+    """
+    if "double_values_0" not in df_ambient:
+        raise KeyError("The DF does not seem to hold barometer data.")
+    df_ambient = df_ambient[df_ambient["double_values_0"] > MINIMUM_PRESSURE_MB]
+    return df_ambient