getMULTI.addpara function

Get Additional Parameters Related to Interval-specific Slopes, Interval-specific Changes and Values of Change-from- baseline for Multivariate Latent Change Score Models

This function derives additional parameters for multivariate latent change score models. It specifies the means and variances of interval-specific slopes, interval-specific changes, and values of change-from-baseline.

getMULTI.addpara(dat, t_var, y_var, curveFun, intrinsic, records, starts)

Arguments

• dat: A wide-format data frame, with each row corresponding to a unique ID. It contains the observed variables with repeated measurements and occasions for multiple longitudinal outcomes. It takes the value passed from getMGM().

• t_var: A vector of strings, with each element representing the prefix for column names related to the time variable for the corresponding outcome variable at each study wave. It takes the value passed from getMGM().

• y_var: A vector of strings, with each element representing the prefix for column names corresponding to a particular outcome variable at each study wave. It takes the value passed from getMGM().

• curveFun: A string specifying the functional form of the growth curve. Supported options for y_model = "LGCM" include: "linear" (or "LIN"), "quadratic" (or "QUAD"), "negative exponential"

  (or "EXP"), "Jenss-Bayley" (or "JB"), and "bilinear spline" (or "BLS"). Supported options for y_model = "LCSM" include: "quadratic" (or "QUAD"), "negative exponential"

  (or "EXP"), "Jenss-Bayley" (or "JB"), and "nonparametric" (or "NonP"). It takes the value passed from getMGM().

• intrinsic: A logical flag indicating whether to build an intrinsically nonlinear longitudinal model. It takes the value passed from getMGM().

• records: A list of numeric vectors, with each vector specifying the indices of the observed study waves for the corresponding outcome variable. It takes the value passed from getMGM().

• starts: A list of initial values for the parameters, either takes the value passed from getMGM() or derived by the helper function getMULTI.initial().

Returns

A list containing the specification of the means and variances of interval-specific slopes, interval-specific changes, and values of change-from-baseline for multivariate latent change score models.