diff --git a/control/tests/xferfcn_test.py b/control/tests/xferfcn_test.py
index 204c6dfd8..0d208c6db 100644
--- a/control/tests/xferfcn_test.py
+++ b/control/tests/xferfcn_test.py
@@ -5,8 +5,8 @@
import unittest
import numpy as np
-from control.statesp import StateSpace, _convertToStateSpace
-from control.xferfcn import TransferFunction, _convertToTransferFunction
+from control.statesp import StateSpace, _convertToStateSpace, rss
+from control.xferfcn import TransferFunction, _convertToTransferFunction, ss2tf
from control.lti import evalfr
from control.exception import slycot_check
# from control.lti import isdtime
@@ -536,6 +536,25 @@ def testMIMO(self):
np.testing.assert_array_almost_equal(H.num[1][0], H2.num[1][0])
np.testing.assert_array_almost_equal(H.den[1][0], H2.den[1][0])
+ def testIndexing(self):
+ tm = ss2tf(rss(5, 3, 3))
+
+ # scalar indexing
+ sys01 = tm[0, 1]
+ np.testing.assert_array_almost_equal(sys01.num[0][0], tm.num[0][1])
+ np.testing.assert_array_almost_equal(sys01.den[0][0], tm.den[0][1])
+
+ # slice indexing
+ sys = tm[:2, 1:3]
+ np.testing.assert_array_almost_equal(sys.num[0][0], tm.num[0][1])
+ np.testing.assert_array_almost_equal(sys.den[0][0], tm.den[0][1])
+ np.testing.assert_array_almost_equal(sys.num[0][1], tm.num[0][2])
+ np.testing.assert_array_almost_equal(sys.den[0][1], tm.den[0][2])
+ np.testing.assert_array_almost_equal(sys.num[1][0], tm.num[1][1])
+ np.testing.assert_array_almost_equal(sys.den[1][0], tm.den[1][1])
+ np.testing.assert_array_almost_equal(sys.num[1][1], tm.num[1][2])
+ np.testing.assert_array_almost_equal(sys.den[1][1], tm.den[1][2])
+
def testMatrixMult(self):
"""MIMO transfer functions should be multiplyable by constant
matrices"""
diff --git a/control/xferfcn.py b/control/xferfcn.py
index e8fe084f8..b8a48c0a7 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -491,6 +491,46 @@ def __pow__(self, other):
if other < 0:
return (TransferFunction([1], [1]) / self) * (self**(other+1))
+ def __getitem__(self, key):
+ key1, key2 = key
+
+ # pre-process
+ if isinstance(key1, int):
+ key1 = slice(key1, key1 + 1, 1)
+ if isinstance(key2, int):
+ key2 = slice(key2, key2 + 1, 1)
+ # dim1
+ start1, stop1, step1 = key1.start, key1.stop, key1.step
+ if step1 is None:
+ step1 = 1
+ if start1 is None:
+ start1 = 0
+ if stop1 is None:
+ stop1 = len(self.num)
+ # dim1
+ start2, stop2, step2 = key2.start, key2.stop, key2.step
+ if step2 is None:
+ step2 = 1
+ if start2 is None:
+ start2 = 0
+ if stop2 is None:
+ stop2 = len(self.num[0])
+
+ num = []
+ den = []
+ for i in range(start1, stop1, step1):
+ num_i = []
+ den_i = []
+ for j in range(start2, stop2, step2):
+ num_i.append(self.num[i][j])
+ den_i.append(self.den[i][j])
+ num.append(num_i)
+ den.append(den_i)
+ if self.isctime():
+ return TransferFunction(num, den)
+ else:
+ return TransferFunction(num, den, self.dt)
+
def evalfr(self, omega):
"""Evaluate a transfer function at a single angular frequency.
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