iir_filters

A Rust re-implementation of some of scipy's digital filters.

Example:

```rust use iirfilters::filterdesign::FilterType; use iirfilters::filterdesign::butter; use iirfilters::sos::zpk2sos; use iirfilters::filter::DirectForm2Transposed; use iir_filters::filter::Filter;

fn main() -> Result<(), Box> { let order = 5; let cutofflow = 1.0; let cutoffhi= 10.0; let fs = 81.0;

let zpk = butter(order, FilterType::BandPass(cutoff_low, cutoff_hi),fs)?;
let sos = zpk2sos(&zpk, None)?;

let mut dft2 = DirectForm2Transposed::new(&sos);
let data:Vec<f64>  = vec![1.0, 2.0, 3.0];

let mut output:Vec<f64> = vec![];

for x in data.iter() {
    output.push( dft2.filter(*x) );
}

return Ok( () );

} ```

See: scipy.signal: butter()

⚠️ For now it only implements Butterworth filters, because that's all I'm interested in.