Wrapper function for gsignal::butter to construct a bandpass (or
low or high pass) filter at a particular frequency. Uses the Sos form for
the filter, which works better numerically particularly for very low
frequencies.
Usage
build_filter(lo = NULL, hi = NULL, sampfreq, order = 13)
Arguments
- lo
Lower frequency cutoff in Hz. If only lo is specified, then
build_filter constructs a high pass filter
- hi
Upper frequency cutoff in Hz. If only hi is specified, then
build_filter constructs a high pass filter
- sampfreq
Sampling frequency for the data in Hz.
- order
(optional) Order for the filter
Value
Filter parameters in Sos form
Examples
# Low pass filter with a cutoff at 0.5Hz for data sampled at 100Hz
lopass <- build_filter(lo=0.5, sampfreq=100)
# Band pass filter that passes frequencies between 0.5 and 10Hz
bandpass <- build_filter(lo=0.5, hi=10, sampfreq=100)