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Classify Static and Moving Samples From Acceleration

Source: R/geomag_calib.R
tag_static.Rd

Computes a logical is_static flag for each row in tag$magnetic using the acceleration magnitude.

The classification is done in three steps:

  1. Compute the acceleration norm gn = sqrt(x^2 + y^2 + z^2) for each sample.

  2. Apply the hard threshold abs(gn - 1) < static_thr_hard to build the initial static candidates.

  3. If tag$acceleration is available, cluster the positive value samples into low- and high-activity groups, force the high-activity group to FALSE, then remove outliers among the remaining candidate static points using a MAD rule with threshold static_thr_outlier.

Usage

tag_static(
  tag,
  static_thr_hard = NULL,
  static_thr_outlier = NULL,
  use_activity = FALSE
)

Arguments

tag

A GeoPressureR tag object containing a $magnetic data frame with acceleration_x, acceleration_y, and acceleration_z. If tag$acceleration is present, its value column is used as an activity signal.

static_thr_hard

Numeric or NULL. Hard threshold around 1 g used to build the initial candidate static set. If NULL, the default 0.15 is used.

static_thr_outlier

Numeric or NULL. MAD threshold used to remove outliers among the candidate static samples. If NULL, the default 3 is used.

use_activity

Logical. If TRUE and tag$acceleration is available, use activity clustering to flag high-activity samples as moving before MAD outlier filtering.

Value

The input tag object with tag$magnetic$is_static added or updated. tag$magnetic$is_static is a logical vector where TRUE denotes samples considered static and FALSE denotes samples considered moving.

Examples

library(GeoPressureR)
withr::with_dir(system.file("extdata", package = "GeoMagR"), {
  tag <- tag_create("14DM", quiet = TRUE)
  tag_static_obj <- tag_static(tag)
  table(tag_static_obj$magnetic$is_static)

  # A stricter hard threshold keeps fewer samples as static
  tag_static_strict <- tag_static(tag, static_thr_hard = 0.05, static_thr_outlier = 2)
  table(tag_static_strict$magnetic$is_static)
})
#> 
#> FALSE  TRUE 
#>   952   998