diff --git a/src/data/Drawable.py b/src/data/Drawable.py
index eaa74cb..b1990f5 100644
--- a/src/data/Drawable.py
+++ b/src/data/Drawable.py
@@ -1,10 +1,5 @@
 # -*- coding: iso-8859-1 -*-
 
-import threading
-
-import numpy as np
-
-
 #############################################################################
 #                                                                           #
 # Name: Class Drawable                                                      #
@@ -106,7 +101,8 @@ class Drawable:
         "Returns labels to be plotted (List)"
         if index in self.text:
             return self.text[index]
-        else: return None
+        else:
+            return None
 
 
     def set_text(self, index, text):
@@ -158,14 +154,14 @@ class Drawable:
 
     def get_ymin(self):
         "Returns minimum of y"
-        if type(self.y)==type([]):
-            return min([l.min() for l in self.y])
+        if isinstance(self.y, list):
+            return min([yarr.min() for yarr in self.y])
         else:
             return self.y.min()
 
     def get_yminpos(self):
         "Returns smallest positive value of y"
-        if type(self.y) == type([]):
+        if isinstance(self.y, list):
             ymins = []
             for ys in self.y:
                 mask = ys > 0
@@ -173,7 +169,7 @@ class Drawable:
             ymin = min(ymins)
         else:
             mask = self.y > 0
-            ymin = y[mask].min()
+            ymin = self.y[mask].min()
         return ymin
 
     def set_ymin(self, ymin):
@@ -182,8 +178,8 @@ class Drawable:
 
     def get_ymax(self):
         "Returns maximimum of y"
-        if type(self.y)==type([]):
-            return max([l.max() for l in self.y])
+        if isinstance(self.y, list):
+            return max([yarr.max() for yarr in self.y])
         else:
             return self.y.max()