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.. _reg-multilevel:
.. currentmodule:: pywt
Multilevel DWT, IDWT and SWT
============================
Multilevel DWT decomposition
----------------------------
>>> import pywt
>>> x = [3, 7, 1, 1, -2, 5, 4, 6]
>>> db1 = pywt.Wavelet('db1')
>>> cA3, cD3, cD2, cD1 = pywt.wavedec(x, db1)
>>> print(cA3)
[ 8.83883476]
>>> print(cD3)
[-0.35355339]
>>> print(cD2)
[ 4. -3.5]
>>> print(cD1)
[-2.82842712 0. -4.94974747 -1.41421356]
>>> pywt.dwt_max_level(len(x), db1)
3
>>> cA2, cD2, cD1 = pywt.wavedec(x, db1, mode='constant', level=2)
Multilevel IDWT reconstruction
------------------------------
>>> coeffs = pywt.wavedec(x, db1)
>>> print(pywt.waverec(coeffs, db1))
[ 3. 7. 1. 1. -2. 5. 4. 6.]
Multilevel SWT decomposition
----------------------------
>>> x = [3, 7, 1, 3, -2, 6, 4, 6]
>>> (cA2, cD2), (cA1, cD1) = pywt.swt(x, db1, level=2)
>>> print(cA1)
[ 7.07106781 5.65685425 2.82842712 0.70710678 2.82842712 7.07106781
7.07106781 6.36396103]
>>> print(cD1)
[-2.82842712 4.24264069 -1.41421356 3.53553391 -5.65685425 1.41421356
-1.41421356 2.12132034]
>>> print(cA2)
[ 7. 4.5 4. 5.5 7. 9.5 10. 8.5]
>>> print(cD2)
[ 3. 3.5 0. -4.5 -3. 0.5 0. 0.5]
>>> [(cA2, cD2)] = pywt.swt(cA1, db1, level=1, start_level=1)
>>> print(cA2)
[ 7. 4.5 4. 5.5 7. 9.5 10. 8.5]
>>> print(cD2)
[ 3. 3.5 0. -4.5 -3. 0.5 0. 0.5]
>>> coeffs = pywt.swt(x, db1)
>>> len(coeffs)
3
>>> pywt.swt_max_level(len(x))
3
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