Bilinear transform and Butterworth filters

mathnet / mathnet-filtering

Math.NET Filtering (formerly Neodym)

http://filtering.mathdotnet.com

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Bilinear transform and Butterworth filters #17

Closed Fylax closed 4 years ago

Fylax commented 5 years ago

Starting from this discussion I am proposing an implementation for the Butterworth filters. In order to make it work, I implemented:

Bilinear transform
Butterworth designer
Butterworth IIR coefficients calculator

In particular, the bilinear tranform should work with any LTI, so it might be possible to implement it inside the base Numerics package, but for sure it will work with any possible future filter implementation.

I have added some unit tests for the designed filters: the expected values have been computed using Octave.

Fylax commented 5 years ago

Travis with mono seems to fail due to missing ValueTuple (that I referenced as nuget package for .NET Framework version < 4.7)

Nevertheless, mono documentation seems to suggest that adding that package should make the trick. Any idea regarding the issue?

cdrnet commented 5 years ago

Thanks!

According to the logs, it seems the problem is that the System.ValueType type is available twice now, once in mscorlib and once in System.ValueTuple. Maybe the problem already goes away if the reference is managed by Paket. I'll have a look.

Fylax commented 5 years ago

Hello.

I managed to let paket handle the System.ValueTuple package (removing it from the project definition). Sadly this did not resolve the problem, but here it seems to be a NetStandard 2.0 related issue.

cdrnet commented 4 years ago

I've finally pulled this into master - thanks a lot!

(pulled in directly, bypassing the PR)