liftfilt
Syntax
Description
liftfilt(___)
with no output arguments plots
the successive biorthogonal pairs. A scaling function and a wavelet comprise
each pair.
Examples
Generate Biorthogonal Wavelet Filters From Haar Filters
This example shows how to obtain the bior1.3
wavelet filters using Haar filters and elementary lifting steps.
Obtain the Haar lowpass decomposition and reconstruction filters.
[LoD,~,LoR,~] = wfilters("haar");
Use liftingStep
to create two elementary lifting steps of type update
. Create an array consisting of the two steps.
els1 = liftingStep(Type="update",... Coefficients=[0.125 -0.125],MaxOrder=0); els2 = liftingStep(Type="update",... Coefficients=[0.125 -0.125],MaxOrder=1); elsBoth = [els1;els2];
Apply the lifting steps to the Haar filters to obtain new filters.
[LoDN,HiDN,LoRN,HiRN] = liftfilt(LoD,LoR,LiftingSteps=elsBoth);
Obtain the bior1.3
wavelet filters. Confirm that up to a sign change, the wavelet filters are equal to the filters liftfilt
returns.
[LoDw,HiDw,LoRw,HiRw] = wfilters("bior1.3"); samewavelet = ... isequal([LoDw,HiDw,LoRw,HiRw],[LoDN,-HiDN,LoRN,HiRN])
samewavelet = logical
1
Use liftfilt
to plot the successive biorthogonal pairs of scaling functions and wavelets.
liftfilt(LoD,LoR,LiftingSteps=elsBoth)
Input Arguments
LoD,LoR
— Lowpass filters
real-valued vectors
Lowpass filters associated with a wavelet, specified as real-valued
vectors. LoD
is the lowpass decomposition filter.
LoR
is the lowpass reconstruction
filters.
Example: For [LoD,~,LoR,~] = wfilters("db4")
,
liftfilt(LoD,LoR,LiftingSteps=lsteps)
applies
the elementary lifting steps specified in lsteps
to
the db4
filters.
Data Types: double
ELS
— Lifting steps
structure array
Lifting steps, specified as a structure array consisting of elementary lifting steps.
If
liftingStep.Type="update"
,LoR
andHiD
are unchanged, whereHiD
is the associated highpass decomposition filter.If
liftingStep.Type="predict"
,LoD
andHiR
are unchanged, whereHiR
is the associated highpass decomposition filter.
Example: liftfilt(LoD,LoR,LiftingSteps=ELS)
applies
the elementary lifting steps specified in lsteps
to
the filters LoD
and
LoR
.
Data Types: struct
NF
— Normalization factor
nonzero scalar
Normalization factor, specified as a nonzero scalar.
Example: [LoDN,HiDN,LoRN,HiRN] =
liftfilt(LoD,LoR,NF=2)
scales the filters by
2.
Data Types: double
Output Arguments
LoDN,HiDN
— Decomposition filters
real-valued vectors
Decomposition filters, returned as a pair of real-valued vectors.
LoDN
and HiDN
correspond to
the lowpass and highpass filters, respectively.
Data Types: double
LoRN,HiRN
— Reconstruction filters
real-valued vectors
Reconstruction filters, returned as a pair of real-valued vectors.
LoRN
and HiRN
correspond to
the lowpass and highpass filters, respectively.
Data Types: double
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
Plotting is not supported.
Version History
Introduced in R2021bR2021b: liftfilt
input syntax has changed
The liftfilt
input syntax has changed. Use name-value
arguments instead.
Functionality | Result | Use Instead | Compatibility Considerations |
---|---|---|---|
[LoDN,HiDN,LoRN,HiRN] =
liftfilt(LoD,HiD,LoR,HiR,ELS) | Errors | [LoDN,HiDN,LoRN,HiRN] =
liftfilt(LoD,LoR,LiftingSteps=ELS) ,
where ELS is a structure array
consisting of elementary lifting steps. | You can also scale the filters by a normalization
factor. For more information about elementary lifting
steps, see liftingStep . |
liftfilt(LoD,HiD,LoR,HiR,ELS,TYPE,VALUE) | Errors | NA | This syntax is no longer supported. |
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