"""
Digital recursive filter.
Implemented using Numba library (JIT high-performance compilation); used to be a precompiled C-package.
"""
import numpy as np
import numba as nb
[docs]@nb.njit(fastmath=False,parallel=False)
def iir_apply_complex(trace, xcoeff, ycoeff):
"""
Apply digital, (possibly) recursive filter with coefficients `xcoeff` and `ycoeff` along the first axis.
Result is filtered signal `y` with ``y[n]=sum_j x[n-j]*xcoeff[j] + sum_k y[n-k-1]*ycoeff[k]``.
"""
new_trace=np.zeros(trace.shape,dtype=trace.dtype)
if len(xcoeff)==0:
return new_trace
nx=len(xcoeff)
ny=len(ycoeff)
tstart=max(nx-1,ny)
new_trace[:tstart]=trace[:tstart]
for i in range(tstart,len(trace)):
for xi in range(nx):
new_trace[i]+=trace[i-xi]*xcoeff[xi]
for yi in range(ny):
new_trace[i]+=new_trace[i-yi-1]*ycoeff[yi]
return new_trace