[SciPy-user] small error in documentation signal.py
Stef Mientki
s.mientki@ru...
Fri Apr 13 16:24:14 CDT 2007
I don't know where to report bugs in scipy package,
and I don't know if errors in documentation are called bugs,
but anyway, here is the bug,
lfilter(b, a, x, axis=-1, zi=None)
<snip>
Algorithm:
The filter function is implemented as a direct II transposed
structure.
This means that the filter implements
y[n] = b[0]*x[n] + b[1]*x[n-1] + ... + b[nb]*x[n-nb]
- a[1]*y[n-1] + ... + a[na]*y[n-na]
should be
y[n] = b[0]*x[n] + b[1]*x[n-1] + ... + b[nb]*x[n-nb]
- a[1]*y[n-1] - ... - a[na]*y[n-na]
or this might even be better
a[0]*y[n] = b[0]*x[n] + b[1]*x[n-1] + ... + b[nb]*x[n-nb]
- a[1]*y[n-1] + ... + a[na]*y[n-na]
cheers,
Stef Mientki
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