Throw exception if all scale factors are 0

Author: zStupan

niaarm/niaarm.py

@@ -36,12 +36,16 @@ def __init__(self, dimension, features, transactions, alpha=0.0, beta=0.0, gamma
         """
         self.features = features
         self.transactions = transactions
+
+        if alpha + beta + gamma + delta == 0:
+            raise ValueError('At least one of alpha, beta, gamma or delta must be set')
+
         self.alpha = alpha
         self.beta = beta
         self.gamma = gamma
         self.delta = delta
-        self.logging = logging
 
+        self.logging = logging
         self.best_fitness = np.NINF
         self.rules = []
         super().__init__(dimension, 0.0, 1.0)