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implement indexing for transfer function #246

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Merged
merged 1 commit into from
Dec 21, 2018
Merged

implement indexing for transfer function #246

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23 changes: 21 additions & 2 deletions control/tests/xferfcn_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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"""
Expand Down
40 changes: 40 additions & 0 deletions control/xferfcn.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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.

Expand Down