1
Denominator a must be 1-D.
Package:
scipy
8546
8546
Exception Class:
ValueError
Raise code
# cases where a ValueError is more appropriate, and it allows
# b to be 2D.
b = np.atleast_1d(b)
if b.ndim != 1:
raise ValueError("Numerator b must be 1-D.")
a = np.atleast_1d(a)
if a.ndim != 1:
raise ValueError("Denominator a must be 1-D.")
while len(a) > 1 and a[0] == 0.0:
a = a[1:]
if a.size < 1:
raise ValueError("There must be at least one nonzero `a` coefficient.")
if a[0] != 1.0:Links to the raise (1)
https://github.com/scipy/scipy/blob/e4b3e6eb372b8c1d875f2adf607630a31e2a609c/scipy/signal/signaltools.py#L3591Ways to fix
2
If a is set to 2D array this error is raised.
How to to recreate the error:
pipenv install scipy numpy
from numpy import array, ones
from scipy.signal import lfilter, lfilter_zi, butter
b, a = butter(5, 0.25)
a = [a]
zi = lfilter_zi(b, a)
y, zo = lfilter(b, a, ones(10), zi=zi)
print(y)
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-33-dbc16574d684> in <module>()
2 from scipy.signal import lfilter, lfilter_zi, butter
3 b, a = butter(5, 0.25)
----> 4 zi = lfilter_zi(b, [a])
5 y, zo = lfilter(b, a, ones(10), zi=zi)
6 print(y)
/usr/local/lib/python3.7/dist-packages/scipy/signal/signaltools.py in lfilter_zi(b, a)
3589 a = np.atleast_1d(a)
3590 if a.ndim != 1:
-> 3591 raise ValueError("Denominator a must be 1-D.")
3592
3593 while len(a) > 1 and a[0] == 0.0:
ValueError: Denominator a must be 1-D.
Fixed:
from numpy import array, ones
from scipy.signal import lfilter, lfilter_zi, butter
b, a = butter(5, 0.25)
# a = [a]
zi = lfilter_zi(b, a)
y, zo = lfilter(b, a, ones(10), zi=zi)
print(y)
[1. 1. 1. 1. 1. 1. 1. 1. 1. 1.]
Aug 26, 2021
Add a possible fix
Please authorize to post fix