Add Butterworth Filter #242
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## master #242 +/- ##
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+ Coverage 92.14% 92.17% +0.02%
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Files 12 12
Lines 1642 1648 +6
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+ Hits 1513 1519 +6
Misses 129 129
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Docs and tests are needed.
Some docstrings in ImageFiltering are written in Julia pre-1.0 age, so you can follow the guideline in https://docs.julialang.org/en/v1/manual/documentation/#man-documentation. I personally prefer a verbose docstring, e.g., the docstring for Gabor in #235. You can also follow how unit tests are written in that PR.
Style fix Co-authored-by: Johnny Chen <[email protected]>
| #Citation | ||
| Selesnick, Ivan W., and C. Sidney Burrus. "Generalized digital Butterworth filter design." IEEE Transactions on signal processing 46.6 (1998): 1688-1694. | ||
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Extra empty line here would cause ?Kernel.butterworth giving nothing.
| @@ -509,6 +509,26 @@ moffat(α::Real, β::Real) = moffat(α, β, ceil(Int, (α*2*sqrt | |||
| sum(x.^2) | |||
| end | |||
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| """ | |||
| butterworth(n,Wn,ls{tuple}) -> k | |||
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indentation, and :: for type annotation.
| butterworth(n,Wn,ls{tuple}) -> k | |
| butterworth(n, Wn, ls::Dims) -> k |
| @@ -509,6 +509,26 @@ moffat(α::Real, β::Real) = moffat(α, β, ceil(Int, (α*2*sqrt | |||
| sum(x.^2) | |||
| end | |||
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| """ | |||
| butterworth(n,Wn,ls{tuple}) -> k | |||
| Returns a multidimensional dimensional Butterworth kernel contained in an OffsetArray(::Matrix{Float64}) | |||
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one extra new line after the signature.
| Returns a multidimensional dimensional Butterworth kernel contained in an OffsetArray(::Matrix{Float64}) | |
| Returns a multidimensional dimensional Butterworth kernel contained in an OffsetArray(::Matrix{Float64}) |
| - `n` is the order of the filter | ||
| - `Wn` is the normalized cutoff frequency | ||
| - `ls` is the size of the kernel |
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You don't need indentation for the markdown list
| - `n` is the order of the filter | |
| - `Wn` is the normalized cutoff frequency | |
| - `ls` is the size of the kernel | |
| - `n` is the order of the filter | |
| - `Wn` is the normalized cutoff frequency | |
| - `ls` is the size of the kernel |
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| - `n` is the order of the filter | ||
| - `Wn` is the normalized cutoff frequency | ||
| - `ls` is the size of the kernel |
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why you use ls for kernel size instead of sz? The former seems to come from the math equation of butterworth kernel. Can you also add the equation to the docstring so that people immediately knows what n, Wn, ls means and how they affects the results?
| @. 1/(1+(sqrt(2)-1)*(df(R)/Wn)^nn) | ||
| end | ||
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| butterworth(n::Real, Wn::Real, ls::Integer) = butterworth(n, Wn, (ls,ls)) |
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This convenient method only makes sense when butterworth is 2D only; otherwise, we should not add it.
| @test Kernel.butterworth(a,b,(3,3)) == Kernel.butterworth(a,b,3) | ||
| @test Kernel.butterworth(a,b,(4,4)) == Kernel.butterworth(a,b,4) |
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We also need some numerical tests here, can you test against one or two results generated from other frameworks that has butterworth implemented or manual calculated results? Also do remember to add a comment on how the references are generated.
We also need to test that the kernel axis are "centered". For instance, the axes should be (-1:1, -1:1) when kernel size is (3, 3). Also need to test the even case as well.
| Selesnick, Ivan W., and C. Sidney Burrus. "Generalized digital Butterworth filter design." IEEE Transactions on signal processing 46.6 (1998): 1688-1694. | ||
| """ | ||
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| function butterworth(n::Real, Wn::Real, ls::Tuple{Integer,Integer}) |
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It looks like if we do
| function butterworth(n::Real, Wn::Real, ls::Tuple{Integer,Integer}) | |
| function butterworth(n::Real, Wn::Real, ls::NTuple{N,Integer}) where N |
we immediately get a N-dimensional implementation as the docstring says: "multidimensional dimensional Butterworth kernel". Can you check this and if it works, add 1d and 3d tests? Also don't forget to update the docstring OffsetArray(::Matrix{Float64}).
In response to feature request #240
Please let me know if there are any fixes to be done on the code.