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Design a Butterworth filter in second-order-sections (SOS) form

Source: R/filters-causal.R
sosDesign.Rd

Builds the cascaded second-order-sections representation of a Butterworth filter directly from the analog prototype poles (bilinear transform), which is numerically stable for all orders. This is the design entry point for the causal / stateful filtering functions (sosfilt, sosfiltfilt, StreamFilter).

Usage

sosDesign(
  low = NULL,
  high = NULL,
  order = 4L,
  type = c("pass", "low", "high", "stop"),
  sr
)

Arguments

low

Lower cutoff frequency in Hz. Required for "high" and "pass"/"stop".

high

Upper cutoff frequency in Hz. Required for "low" and "pass"/"stop".

order

Filter order (per band). Default 4.

type

Filter type: "low", "high", "pass" (bandpass), or "stop" (bandstop).

sr

Sampling rate in Hz.

Value

A numeric matrix with one second-order section per row and six columns c(b0, b1, b2, a0, a1, a2).

See also

sosfilt, sosfiltfilt, StreamFilter

Examples

sos <- sosDesign(high = 40, type = "low", sr = 250, order = 4)
y <- sosfilt(sos, rnorm(1000))