From dce14e6412a41ea8e912bac86ac53d9739fd3f72 Mon Sep 17 00:00:00 2001
From: ggventurini <ggventurini+GITHUB@gmail.com>
Date: Fri, 5 Jun 2015 15:05:59 +0200
Subject: [PATCH] Bugfix: import missing

---
 deltasigma/_simulateQDSM.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/deltasigma/_simulateQDSM.py b/deltasigma/_simulateQDSM.py
index b90365c..7ab4bbd 100644
--- a/deltasigma/_simulateQDSM.py
+++ b/deltasigma/_simulateQDSM.py
@@ -25,7 +25,7 @@
 import scipy
 
 from scipy.linalg import lstsq
-from scipy.signal import freqz
+from scipy.signal import freqz, tf2zpk
 
 from ._ds_quantize import ds_quantize
 from ._evalTF import evalTF
@@ -119,7 +119,7 @@ def simulateQDSM(u, arg2, nlev=2, x0=None):
         form = 1
         order = ABCD.shape[0] - nq
     elif _is_num_den(arg2):
-        zeros, poles, k = tf2zpk(*arg)
+        zeros, poles, k = tf2zpk(*arg2)
         form = 2
         order = max(zeros.shape)
     else: