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allow string input in dwt_max_level #269

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Merged
merged 1 commit into from
Jan 15, 2017
Merged

allow string input in dwt_max_level #269

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36 changes: 32 additions & 4 deletions pywt/_dwt.py
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Original file line number Diff line number Diff line change
@@ -1,12 +1,22 @@
import sys
import numpy as np
from numbers import Number

from ._extensions._pywt import Wavelet, Modes, _check_dtype

from ._extensions._pywt import (Wavelet, Modes, _check_dtype, wavelist)
from ._extensions._dwt import (dwt_single, dwt_axis, idwt_single, idwt_axis,
upcoef as _upcoef, downcoef as _downcoef,
dwt_max_level as _dwt_max_level,
dwt_coeff_len as _dwt_coeff_len)

__all__ = ["dwt", "idwt", "downcoef", "upcoef", "dwt_max_level", "dwt_coeff_len"]
__all__ = ["dwt", "idwt", "downcoef", "upcoef", "dwt_max_level",
"dwt_coeff_len"]

# define string_types as in six for Python 2/3 compatibility
if sys.version_info[0] == 3:
string_types = str,
else:
string_types = basestring,


def dwt_max_level(data_len, filter_len):
Expand All @@ -19,8 +29,9 @@ def dwt_max_level(data_len, filter_len):
----------
data_len : int
Input data length.
filter_len : int
Wavelet filter length.
filter_len : int, str or Wavelet
The wavelet filter length. Alternatively, the name of a discrete
wavelet or a Wavelet object can be specified.

Returns
-------
Expand All @@ -35,9 +46,26 @@ def dwt_max_level(data_len, filter_len):
6
>>> pywt.dwt_max_level(1000, w)
6
>>> pywt.dwt_max_level(1000, 'sym5')
6
"""
if isinstance(filter_len, Wavelet):
filter_len = filter_len.dec_len
elif isinstance(filter_len, string_types):
if filter_len in wavelist(kind='discrete'):
filter_len = Wavelet(filter_len).dec_len
else:
raise ValueError(
("'{}', is not a recognized discrete wavelet. A list of "
"supported wavelet names can be obtained via "
"pywt.wavelist(kind='discrete')").format(filter_len))
elif not (isinstance(filter_len, Number) and filter_len % 1 == 0):
raise ValueError(
"filter_len must be an integer, discrete Wavelet object, or the "
"name of a discrete wavelet.")

if filter_len < 2:
raise ValueError("invalid wavelet filter length")

return _dwt_max_level(data_len, filter_len)

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14 changes: 14 additions & 0 deletions pywt/tests/test__pywt.py
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Original file line number Diff line number Diff line change
Expand Up @@ -106,8 +106,22 @@ def test_dwt_max_level():
assert_(pywt.dwt_max_level(16, 8) == 1)
assert_(pywt.dwt_max_level(16, 9) == 1)
assert_(pywt.dwt_max_level(16, 10) == 0)
assert_(pywt.dwt_max_level(16, np.int8(10)) == 0)
assert_(pywt.dwt_max_level(16, 10.) == 0)
assert_(pywt.dwt_max_level(16, 18) == 0)

# accepts discrete Wavelet object or string as well
assert_(pywt.dwt_max_level(32, pywt.Wavelet('sym5')) == 1)
assert_(pywt.dwt_max_level(32, 'sym5') == 1)

# string input that is not a discrete wavelet
assert_raises(ValueError, pywt.dwt_max_level, 16, 'mexh')

# filter_len must be an integer >= 2
assert_raises(ValueError, pywt.dwt_max_level, 16, 1)
assert_raises(ValueError, pywt.dwt_max_level, 16, -1)
assert_raises(ValueError, pywt.dwt_max_level, 16, 3.3)


def test_ContinuousWavelet_errs():
assert_raises(ValueError, pywt.ContinuousWavelet, 'qwertz')
Expand Down