detect_direction: Detect the direction of a response signal

In mnirs: Muscle Near-Infrared Spectroscopy Processing and Analysis

Detect the direction of a response signal

Description

Resolves whether a signal responds upward ("positive") or downward ("negative") by comparing the excursions of x above and below its initial baseline, taken as the median of the earliest samples ordered by t. The dominant excursion captures the primary response direction even when a fast initial component partially recovers over most of the record (e.g. biexponential drop-recovery), where a net slope would misreport the trend. Used internally to disambiguate peak (maximum) from trough (minimum) detection when direction = "auto".

Usage

detect_direction(
  x,
  t = seq_along(x),
  fallback = x,
  direction = c("auto", "positive", "negative")
)

Arguments

x	A numeric vector of the response variable.
t	An optional numeric vector of the predictor variable (e.g. time). Default is seq_along(x).
fallback	A numeric vector (defaults to x) used to resolve direction when the excursions above and below baseline tie (e.g. flat or symmetric data). The absolute maximum and minimum of fallback are compared; if abs(max) >= abs(min), "positive" is returned.
direction	A character string specifying the response direction to detect when "auto" (default). When "positive" or "negative" returns unchanged.

Value

A character string: "positive" or "negative".

mnirs documentation built on Sept. 13, 2026, 1:06 a.m.