mmParameters: Compute the marker movement parameters speed, onset-speed,...

In axzinker/blenderFace: Collection of functions to process blender measured facial movement data

Compute the marker movement parameters speed, onset-speed, intensity (amplitude), irregularites (onset, apex, offset-phases), symmetry)

Description

Output Parameters:

Usage

mmParameters(
  data,
  colNames,
  colNameSubj,
  colNameFrames,
  mmCutoff = NA,
  verbose = FALSE
)

Arguments

data	Dataframe containing the data with the columns subject, Frame and marker names labeled according to the blenderFace-method (e.g., CL7_x, CL7_y, CR7_x, CR7_y; to compute symmetry values). If the dataframe provides values on the z-axis (e.g., CL7_z), the eukledian distances (3D) are computed instead of the pythagorean distances (2D) to determine marker movement parameters.
colNames	Character vector with marker names of the columns for which the parameters should be computed. A touple or triplet of axes per marker is needed (e.g., CL7_x, CL7_y or CL7_x, CL7_y, CL7_z) to compute parameters. Mirrord markers (e.g., CL7_x, CL7_y and CR7_x, CR7_y) are needed to compute symmetry values.
colNameSubj	Character vector with a single value containig the name of the subject column of the data data-frame.
colNameFrames	Character vector containing the column name of the frames column of the data data-frame
mmCutoff	Cutoff for defining a marker movement: It is only regarded to be a movement, if the distance from t to t+1 is larger than the value of mmCutoff. If NA (default) mmCutoff is computed by the mean + 2SDs of the first 10 frames. However, it can be set to any value, e.g., to .5, which means a distance of .5 mm if data was scaled to mm via the function bu2mm. If movement is smaller than mmCutoff, it is regarded to be an apex-phase or no movement.
verbose	If TRUE, the function prints verbose output. Otherwise not. Default is FALSE.

Details

Speed (sp): Mean distance from frame t to t+1

Onset-Speed (onSp): Mean distance from frame t to t+1 only for movement onset phases (see irregularities)

Intensity/Amplitude (int): Mean of the 20 maximal distances from the first frame of data (= first frame is seen as baseline). Probably use centerCond in advance.

Irregularities (irr): A movement has to be larger than measurement noise and is defined to be larger than the baseline of .5 (which is .5 mm, if function bu2mm is used beforehand). An onset-phase occurs, if the distance between t+1 and t+2 is larger than the distance between t and t+1 (previous frame). An apex-phase is defined by the distance between t and t+1 stays whithin the baseline, independent of the direction of movement. An offset-phase occurs, if the distance between t+1 and t+2 is smaller than the distance between t and t+1 (previous frame). Every change in phases is counted. Because the analysed episodes have different numbers of frames per participant, the relative number of onset, apex, and offset-phases is computed.

Symmetry (sym): Mean correlation (aggregated over axes x,y, and z) of symmetrical markers. Symmetrical markers are determined by their label, e.g., if there is a marker label CL7 (for left mouth corner), it is tests if there is also a marker labeled CR7 (for right mouth corner). If this is true, the markers CL7 and CR7 are regarded to be symmetrical.

Value

returns dataframe containing the marker movement parameters (speed, onst-speed, intensity, irregularities, symmetry) per subject.

Author(s)

Axel Zinkernagel [e-mail]

Examples

markers <- c("CL7_x", "CL7_y", "CL7_z", "CR7_x", "CR7_y", "CR7_z")
myParams <- mmParameters(dataSmm, colNames = markers,
 colNameSubj = "subject",
  colNameFrames = "Frame",
  verbose = TRUE)
myParams

axzinker/blenderFace documentation built on Feb. 27, 2024, 10:25 a.m.