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Merged
merged 16 commits into from
Mar 25, 2023
Merged

Feature print zpk #869

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5c85459
Add print zpk form
henklaak Feb 21, 2023
57620f1
Fix unittest
henklaak Feb 21, 2023
b36732d
Add fix for precision noise
henklaak Feb 21, 2023
45b5ae4
Cleanup unittest
henklaak Feb 21, 2023
07a859d
Merge branch 'python-control:main' into feature_print_zpk
henklaak Feb 24, 2023
93f7b46
Rework after review
henklaak Feb 24, 2023
d2807b0
Shouldn't have commited the pyproject.toml, revering
henklaak Feb 24, 2023
5652bf0
Fix variable mixup due to inconsistent naming
henklaak Feb 24, 2023
58e9d63
Fix variable mixup due to inconsistent naming
henklaak Feb 24, 2023
521a306
Typos
henklaak Feb 24, 2023
2644874
Add default for xferfcn.display_format
henklaak Feb 25, 2023
8101b31
Update after failed tests
henklaak Feb 25, 2023
8d7ac56
Add default for xferfcn.floating_point_format
henklaak Feb 25, 2023
2ca47e1
Fix improper way of setting defaults in test
henklaak Feb 25, 2023
5f506b2
Merge branch 'python-control:main' into feature_print_zpk
henklaak Mar 5, 2023
6933973
update xferfcn._float2str to be more pythonic per @ilayn
murrayrm Mar 25, 2023
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127 changes: 125 additions & 2 deletions control/tests/xferfcn_test.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,9 @@

import control as ct
from control import StateSpace, TransferFunction, rss, evalfr
from control import ss, ss2tf, tf, tf2ss
from control import isctime, isdtime, sample_system, defaults
from control import ss, ss2tf, tf, tf2ss, zpk
from control import isctime, isdtime, sample_system
from control import defaults, reset_defaults, set_defaults
from control.statesp import _convert_to_statespace
from control.xferfcn import _convert_to_transfer_function
from control.tests.conftest import slycotonly, matrixfilter
Expand Down Expand Up @@ -906,6 +907,128 @@ def test_printing_mimo(self):
assert isinstance(str(sys), str)
assert isinstance(sys._repr_latex_(), str)

@pytest.mark.parametrize(
"zeros, poles, gain, output",
[([0], [-1], 1,
'\n'
' s\n'
'-----\n'
's + 1\n'),
([-1], [-1], 1,
'\n'
's + 1\n'
'-----\n'
's + 1\n'),
([-1], [1], 1,
'\n'
's + 1\n'
'-----\n'
's - 1\n'),
([1], [-1], 1,
'\n'
's - 1\n'
'-----\n'
's + 1\n'),
([-1], [-1], 2,
'\n'
'2 (s + 1)\n'
'---------\n'
' s + 1\n'),
([-1], [-1], 0,
'\n'
'0\n'
'-\n'
'1\n'),
([-1], [1j, -1j], 1,
'\n'
' s + 1\n'
'-----------------\n'
'(s - 1j) (s + 1j)\n'),
([4j, -4j], [2j, -2j], 2,
'\n'
'2 (s - 4j) (s + 4j)\n'
'-------------------\n'
' (s - 2j) (s + 2j)\n'),
([1j, -1j], [-1, -4], 2,
'\n'
'2 (s - 1j) (s + 1j)\n'
'-------------------\n'
' (s + 1) (s + 4)\n'),
([1], [-1 + 1j, -1 - 1j], 1,
'\n'
' s - 1\n'
'-------------------------\n'
'(s + (1-1j)) (s + (1+1j))\n'),
([1], [1 + 1j, 1 - 1j], 1,
'\n'
' s - 1\n'
'-------------------------\n'
'(s - (1+1j)) (s - (1-1j))\n'),
])
def test_printing_zpk(self, zeros, poles, gain, output):
"""Test _tf_polynomial_to_string for constant systems"""
G = zpk(zeros, poles, gain, display_format='zpk')
res = str(G)
assert res == output

@pytest.mark.parametrize(
"zeros, poles, gain, format, output",
[([1], [1 + 1j, 1 - 1j], 1, ".2f",
'\n'
' 1.00\n'
'-------------------------------------\n'
'(s + (1.00-1.41j)) (s + (1.00+1.41j))\n'),
([1], [1 + 1j, 1 - 1j], 1, ".3f",
'\n'
' 1.000\n'
'-----------------------------------------\n'
'(s + (1.000-1.414j)) (s + (1.000+1.414j))\n'),
([1], [1 + 1j, 1 - 1j], 1, ".6g",
'\n'
' 1\n'
'-------------------------------------\n'
'(s + (1-1.41421j)) (s + (1+1.41421j))\n')
])
def test_printing_zpk_format(self, zeros, poles, gain, format, output):
"""Test _tf_polynomial_to_string for constant systems"""
G = tf([1], [1,2,3], display_format='zpk')

set_defaults('xferfcn', floating_point_format=format)
res = str(G)
reset_defaults()

assert res == output

@pytest.mark.parametrize(
"num, den, output",
[([[[11], [21]], [[12], [22]]],
[[[1, -3, 2], [1, 1, -6]], [[1, 0, 1], [1, -1, -20]]],
('\n'
'Input 1 to output 1:\n'
' 11\n'
'---------------\n'
'(s - 2) (s - 1)\n'
'\n'
'Input 1 to output 2:\n'
' 12\n'
'-----------------\n'
'(s - 1j) (s + 1j)\n'
'\n'
'Input 2 to output 1:\n'
' 21\n'
'---------------\n'
'(s - 2) (s + 3)\n'
'\n'
'Input 2 to output 2:\n'
' 22\n'
'---------------\n'
'(s - 5) (s + 4)\n'))])
def test_printing_zpk_mimo(self, num, den, output):
"""Test _tf_polynomial_to_string for constant systems"""
G = tf(num, den, display_format='zpk')
res = str(G)
assert res == output

@slycotonly
def test_size_mismatch(self):
"""Test size mismacht"""
Expand Down
135 changes: 113 additions & 22 deletions control/xferfcn.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -69,7 +69,14 @@


# Define module default parameter values
_xferfcn_defaults = {}
_xferfcn_defaults = {
'xferfcn.display_format': 'poly',
'xferfcn.floating_point_format': '.4g'
}

def _float2str(value):
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I would suggest against doing this. It's anti-pattern for Python and also there is a simpler way to grab the default at the code level and reuse.

>>> _num_format = config.defaults.get('xferfcn.floating_point_format', ':.4g')
>>> print(f"Bla {0.232654684684654654:{_num_format}}")
Bla 0.232655

So you don't need to inject f-string machinery to the string representation.

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@henklaak If you can fix up this final issue, I think this PR is ready to post.

_num_format = config.defaults.get('xferfcn.floating_point_format', ':.4g')
return f"{value:{_num_format}}"


class TransferFunction(LTI):
Expand All @@ -92,6 +99,10 @@ class TransferFunction(LTI):
time, positive number is discrete time with specified
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I can't suggest changes above this line so I am suggsting them here:

_xferfcn_defaults = {
    'xferfcn.display_format': 'poly',
    }

sampling time, None indicates unspecified timebase (either
continuous or discrete time).
display_format: None, 'poly' or 'zpk'
Set the display format used in printing the TransferFunction object.
Default behavior is polynomial display and can be changed by
changing config.defaults['xferfcn.display_format'].

Attributes
----------
Expand Down Expand Up @@ -198,6 +209,17 @@ def __init__(self, *args, **kwargs):
#
# Process keyword arguments
#
# During module init, TransferFunction.s and TransferFunction.z
# get initialized when defaults are not fully initialized yet.
# Use 'poly' in these cases.

self.display_format = kwargs.pop(
'display_format',
config.defaults.get('xferfcn.display_format', 'poly'))

if self.display_format not in ('poly', 'zpk'):
raise ValueError("display_format must be 'poly' or 'zpk',"
" got '%s'" % self.display_format)

# Determine if the transfer function is static (needed for dt)
static = True
Expand Down Expand Up @@ -432,22 +454,29 @@ def _truncatecoeff(self):
[self.num, self.den] = data

def __str__(self, var=None):
"""String representation of the transfer function."""
"""String representation of the transfer function.

mimo = self.ninputs > 1 or self.noutputs > 1
Based on the display_format property, the output will be formatted as
either polynomials or in zpk form.
"""
mimo = not self.issiso()
if var is None:
# TODO: replace with standard calls to lti functions
var = 's' if self.dt is None or self.dt == 0 else 'z'
var = 's' if self.isctime() else 'z'
outstr = ""

for i in range(self.ninputs):
for j in range(self.noutputs):
for ni in range(self.ninputs):
for no in range(self.noutputs):
if mimo:
outstr += "\nInput %i to output %i:" % (i + 1, j + 1)
outstr += "\nInput %i to output %i:" % (ni + 1, no + 1)

# Convert the numerator and denominator polynomials to strings.
numstr = _tf_polynomial_to_string(self.num[j][i], var=var)
denstr = _tf_polynomial_to_string(self.den[j][i], var=var)
if self.display_format == 'poly':
numstr = _tf_polynomial_to_string(self.num[no][ni], var=var)
denstr = _tf_polynomial_to_string(self.den[no][ni], var=var)
elif self.display_format == 'zpk':
z, p, k = tf2zpk(self.num[no][ni], self.den[no][ni])
numstr = _tf_factorized_polynomial_to_string(z, gain=k, var=var)
denstr = _tf_factorized_polynomial_to_string(p, var=var)

# Figure out the length of the separating line
dashcount = max(len(numstr), len(denstr))
Expand All @@ -461,10 +490,9 @@ def __str__(self, var=None):

outstr += "\n" + numstr + "\n" + dashes + "\n" + denstr + "\n"

# See if this is a discrete time system with specific sampling time
if not (self.dt is None) and type(self.dt) != bool and self.dt > 0:
# TODO: replace with standard calls to lti functions
outstr += "\ndt = " + self.dt.__str__() + "\n"
# If this is a strict discrete time system, print the sampling time
if type(self.dt) != bool and self.isdtime(strict=True):
outstr += "\ndt = " + str(self.dt) + "\n"

return outstr

Expand All @@ -485,7 +513,7 @@ def __repr__(self):
def _repr_latex_(self, var=None):
"""LaTeX representation of transfer function, for Jupyter notebook"""

mimo = self.ninputs > 1 or self.noutputs > 1
mimo = not self.issiso()

if var is None:
# ! TODO: replace with standard calls to lti functions
Expand All @@ -496,18 +524,23 @@ def _repr_latex_(self, var=None):
if mimo:
out.append(r"\begin{bmatrix}")

for i in range(self.noutputs):
for j in range(self.ninputs):
for no in range(self.noutputs):
for ni in range(self.ninputs):
# Convert the numerator and denominator polynomials to strings.
numstr = _tf_polynomial_to_string(self.num[i][j], var=var)
denstr = _tf_polynomial_to_string(self.den[i][j], var=var)
if self.display_format == 'poly':
numstr = _tf_polynomial_to_string(self.num[no][ni], var=var)
denstr = _tf_polynomial_to_string(self.den[no][ni], var=var)
elif self.display_format == 'zpk':
z, p, k = tf2zpk(self.num[no][ni], self.den[no][ni])
numstr = _tf_factorized_polynomial_to_string(z, gain=k, var=var)
denstr = _tf_factorized_polynomial_to_string(p, var=var)

numstr = _tf_string_to_latex(numstr, var=var)
denstr = _tf_string_to_latex(denstr, var=var)

out += [r"\frac{", numstr, "}{", denstr, "}"]

if mimo and j < self.noutputs - 1:
if mimo and ni < self.ninputs - 1:
out.append("&")

if mimo:
Expand Down Expand Up @@ -1285,7 +1318,7 @@ def _tf_polynomial_to_string(coeffs, var='s'):
N = len(coeffs) - 1

for k in range(len(coeffs)):
coefstr = '%.4g' % abs(coeffs[k])
coefstr = _float2str(abs(coeffs[k]))
power = (N - k)
if power == 0:
if coefstr != '0':
Expand Down Expand Up @@ -1323,6 +1356,48 @@ def _tf_polynomial_to_string(coeffs, var='s'):
return thestr


def _tf_factorized_polynomial_to_string(roots, gain=1, var='s'):
"""Convert a factorized polynomial to a string"""

if roots.size == 0:
return _float2str(gain)

factors = []
for root in sorted(roots, reverse=True):
if np.isreal(root):
if root == 0:
factor = f"{var}"
factors.append(factor)
elif root > 0:
factor = f"{var} - {_float2str(np.abs(root))}"
factors.append(factor)
else:
factor = f"{var} + {_float2str(np.abs(root))}"
factors.append(factor)
elif np.isreal(root * 1j):
if root.imag > 0:
factor = f"{var} - {_float2str(np.abs(root))}j"
factors.append(factor)
else:
factor = f"{var} + {_float2str(np.abs(root))}j"
factors.append(factor)
else:
if root.real > 0:
factor = f"{var} - ({_float2str(root)})"
factors.append(factor)
else:
factor = f"{var} + ({_float2str(-root)})"
factors.append(factor)

multiplier = ''
if round(gain, 4) != 1.0:
multiplier = _float2str(gain) + " "

if len(factors) > 1 or multiplier:
factors = [f"({factor})" for factor in factors]

return multiplier + " ".join(factors)

def _tf_string_to_latex(thestr, var='s'):
""" make sure to superscript all digits in a polynomial string
and convert float coefficients in scientific notation
Expand Down Expand Up @@ -1486,6 +1561,10 @@ def tf(*args, **kwargs):
Polynomial coefficients of the numerator
den: array_like, or list of list of array_like
Polynomial coefficients of the denominator
display_format: None, 'poly' or 'zpk'
Set the display format used in printing the TransferFunction object.
Default behavior is polynomial display and can be changed by
changing config.defaults['xferfcn.display_format']..

Returns
-------
Expand Down Expand Up @@ -1538,7 +1617,7 @@ def tf(*args, **kwargs):

>>> # Create a variable 's' to allow algebra operations for SISO systems
>>> s = tf('s')
>>> G = (s + 1)/(s**2 + 2*s + 1)
>>> G = (s + 1) / (s**2 + 2*s + 1)

>>> # Convert a StateSpace to a TransferFunction object.
>>> sys_ss = ss("1. -2; 3. -4", "5.; 7", "6. 8", "9.")
Expand Down Expand Up @@ -1609,12 +1688,24 @@ def zpk(zeros, poles, gain, *args, **kwargs):
name : string, optional
System name (used for specifying signals). If unspecified, a generic
name <sys[id]> is generated with a unique integer id.
display_format: None, 'poly' or 'zpk'
Set the display format used in printing the TransferFunction object.
Default behavior is polynomial display and can be changed by
changing config.defaults['xferfcn.display_format'].

Returns
-------
out: :class:`TransferFunction`
Transfer function with given zeros, poles, and gain.

Examples
--------
>>> from control import tf
>>> G = zpk([1],[2, 3], gain=1, display_format='zpk')
>>> G
s - 1
---------------
(s - 2) (s - 3)
"""
num, den = zpk2tf(zeros, poles, gain)
return TransferFunction(num, den, *args, **kwargs)
Expand Down