rcond_filter_ar | R Documentation |
Test whether the filter is numerically stable for filtfilt
.
rcond_filter_ar(a)
a |
auto-regression coefficient, numerical vector; the first element must not be zero |
Reciprocal condition number of matrix z1
, used in
filtfilt
. If the number is less than
.Machine$double.eps
, then filtfilt
will fail.
check_filter
# Butterworth filter with low-pass at 0.1 Hz (order = 4)
filter <- butter(4, 0.1, "low")
# TRUE
rcond_filter_ar(filter$a) > .Machine$double.eps
diagnose_filter(filter$b, filter$a, 500)
# Bad filter (order is too high)
filter <- butter(50, 0.1, "low")
rcond_filter_ar(filter$a) > .Machine$double.eps
# filtfilt needs to inverse a singular matrix
diagnose_filter(filter$b, filter$a, 500)
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