diff --git a/Code/S_get_symbolic_expr_error.py b/Code/S_get_symbolic_expr_error.py
index 3b0a95d..a45b106 100644
--- a/Code/S_get_symbolic_expr_error.py
+++ b/Code/S_get_symbolic_expr_error.py
@@ -32,7 +32,10 @@ def get_symbolic_expr_error(pathdir,filename,expr):
         return 1000000
     else:
         try:
-            return np.sqrt(np.mean((f(*real_variables)[good_idx]-data[good_idx][:,-1])**2))/np.sqrt(np.mean(data[good_idx][:,-1]**2))
+            #return np.sqrt(np.mean((f(*real_variables)[good_idx]-data[good_idx][:,-1])**2))/np.sqrt(np.mean(data[good_idx][:,-1]**2))
+            return np.mean(np.log2(1+abs(f(*real_variables)[good_idx]-data[good_idx][:,-1])*2**30))
         except:
             # use this for the case in which the expression is just one number (i.e. not array)
-            return np.sqrt(np.mean((f(*real_variables)-data[:,-1])**2))/np.sqrt(np.mean(data[:,-1]**2))
+            #return np.sqrt(np.mean((f(*real_variables)-data[:,-1])**2))/np.sqrt(np.mean(data[:,-1]**2))
+            return np.mean(np.log2(1+abs(f(*real_variables)-data[:,-1])*2**30))
+