Resolve "Minimal sample size in train-, val, test-set"

Closes #76 (closed)

src/data_handling/data_preparation.py

@@ -353,7 +353,8 @@ class DataPrep(object):
             non_nan_observation = self.observation.dropna(dim=dim)
             intersect = reduce(np.intersect1d, (non_nan_history.coords[dim].values, non_nan_label.coords[dim].values, non_nan_observation.coords[dim].values))
 
-        if len(intersect) == 0:
+        min_length = self.kwargs.get("min_length", 0)
+        if len(intersect) < max(min_length, 1):
             self.history = None
             self.label = None
             self.observation = None