Raise a warning if there are nan values in the weather data set

windpowerlib/modelchain.py

@@ -8,8 +8,7 @@
 """
 import logging
 import pandas as pd
-from windpowerlib import (wind_speed, density, temperature, power_output,
-                          tools)
+from windpowerlib import wind_speed, density, temperature, power_output, tools
 
 
 class ModelChain(object):
@@ -511,10 +510,7 @@ def run_model(self, weather_df):
         'wind_speed'
 
         """
-        # Convert data heights to integer. In some case they are strings.
-        weather_df.columns = pd.MultiIndex.from_arrays([
-            weather_df.columns.get_level_values(0),
-            pd.to_numeric(weather_df.columns.get_level_values(1))])
+        weather_df = tools.check_weather_data(weather_df)
 
         wind_speed_hub = self.wind_speed_hub(weather_df)
         density_hub = (

windpowerlib/tools.py

@@ -7,6 +7,7 @@
 """
 import numpy as np
 import warnings
+import pandas as pd
 
 
 class WindpowerlibUserWarning(UserWarning):
@@ -221,3 +222,30 @@ def estimate_turbulence_intensity(height, roughness_length):
 
     """
     return 1 / (np.log(height / roughness_length))
+
+
+def check_weather_data(weather_df):
+    """
+    Check weather Data Frame.
+
+    - Raise warning if there are nan values.
+    - Convert columns if heights are string and not numeric.
+
+    """
+    # Convert data heights to integer. In some case they are strings.
+    weather_df.columns = pd.MultiIndex.from_arrays(
+        [
+            weather_df.columns.get_level_values(0),
+            pd.to_numeric(weather_df.columns.get_level_values(1)),
+        ]
+    )
+
+    # check for nan values
+    if weather_df.isnull().any().any():
+        nan_columns = list(weather_df.columns[weather_df.isnull().any()])
+        msg = (
+            "The following columns of the weather data contain invalid "
+            "values like 'nan': {0}"
+        )
+        warnings.warn(msg.format(nan_columns), WindpowerlibUserWarning)
+    return weather_df

windpowerlib/turbine_cluster_modelchain.py

@@ -10,7 +10,7 @@
 import logging
 import pandas as pd
 from windpowerlib import wake_losses
-from windpowerlib.modelchain import ModelChain
+from windpowerlib.modelchain import ModelChain, tools
 
 
 class TurbineClusterModelChain(ModelChain):
@@ -289,10 +289,7 @@ def run_model(self, weather_df):
         'wind_speed'
 
         """
-        # Convert data heights to integer. In some case they are strings.
-        weather_df.columns = pd.MultiIndex.from_arrays([
-            weather_df.columns.get_level_values(0),
-            pd.to_numeric(weather_df.columns.get_level_values(1))])
+        weather_df = tools.check_weather_data(weather_df)
 
         self.assign_power_curve(weather_df)
         self.power_plant.mean_hub_height()