Added accommodations for empty dataframes in diffusive (#735)

* Added accommodations for empty dataframes in diffusive

* Changed datatype to numerical arrays from data frames

* Fixed bug

src/model_DAforcing.py

@@ -718,12 +718,21 @@ def _write_lite_restart(
         waterbodies_df = values['waterbody_df']
         waterbodies_ids = values['waterbody_df_ids']
 
-        waterbodies_df = pd.DataFrame(data=waterbodies_df.reshape(len(waterbodies_ids), -1), 
+        # check for empty waterbody df
+        if (len(waterbodies_df)==0):
+
+            waterbodies_df = pd.DataFrame()
+
+        else:
+
+            waterbodies_df = pd.DataFrame(data=waterbodies_df.reshape(len(waterbodies_ids), -1), 
                                       index=waterbodies_ids,
                                       columns=['ifd','LkArea','LkMxE','OrificeA','OrificeC','OrificeE',
                                                'WeirC','WeirE','WeirL','lon', 'lat', 'crs','qd0','h0','index'])
-        waterbodies_df.index.name = 'lake_id'
-        waterbodies_df.drop(columns=['lon', 'lat', 'crs'], inplace=True)
+
+            waterbodies_df.index.name = 'lake_id'
+            waterbodies_df.drop(columns=['lon', 'lat', 'crs'], inplace=True)
+
         timestamp = t0 + timedelta(seconds=values['t-route_model_time'])
 
         # create restart filenames
@@ -829,7 +838,12 @@ def write_flowveldepth_netcdf(values,
 
     ndg_columns = [(j+1,'ndg') for j in range(nsteps)]
     # renaming nudge columns
-    nudge.columns = ndg_columns
+
+    if (nudge.empty):
+        nudge = pd.DataFrame(columns=ndg_columns)
+    else:
+        nudge.columns = ndg_columns
+
     # Left joining qvd and nudge values on index
     qvd_ndg = pd.merge(qvd_ndg, nudge, left_index=True, right_index=True, how='left')
 

src/troute_model.py

@@ -101,10 +101,15 @@ def preprocess_static_vars(self, values: dict):
             from_files=False, value_dict=values,
             bmi_parameters=self._bmi_parameters,)
 
-        values['diffusive_tw_ids'] = self._network._nexus_latlon.id.values
-        values['diffusive_tw_latitude'] = self._network._nexus_latlon.lat.values
-        values['diffusive_tw_longitude'] = self._network._nexus_latlon.lon.values
-
+        if (len(self._network._nexus_latlon) > 0):
+            values['diffusive_tw_ids'] = self._network._nexus_latlon.id.values
+            values['diffusive_tw_latitude'] = self._network._nexus_latlon.lat.values
+            values['diffusive_tw_longitude'] = self._network._nexus_latlon.lon.values
+        else:
+            values['diffusive_tw_ids'] = np.empty(0,dtype=np.int32)
+            values['diffusive_tw_latitude'] = np.empty(0,dtype=np.float64)
+            values['diffusive_tw_longitude'] = np.empty(0,dtype=np.float64)        
+
         # Create data assimilation object with IDs but no dynamic variables yet.
         # Dynamic variables will be assigned during 'run' function. 
         self._data_assimilation = tr.DataAssimilation(