Examples of Longitudinal Models with Time-varying Covariates

In nlpsem: Linear and Nonlinear Longitudinal Process in Structural Equation Modeling Framework

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

Load nlpsem package, dependent packages and set CSOLNP as the optimizer

library(nlpsem)
mxOption(model = NULL, key = "Default optimizer", "CSOLNP", reset = FALSE)

Load pre-computed models

load(system.file("extdata", "getTVCmodel_examples.RData", package = "nlpsem"))

Load example data and preprocess data

# Load ECLS-K (2011) data
data("RMS_dat")
RMS_dat0 <- RMS_dat
# Re-baseline the data so that the estimated initial status is for the
# starting point of the study
baseT <- RMS_dat0$T1
RMS_dat0$T1 <- (RMS_dat0$T1 - baseT)/12
RMS_dat0$T2 <- (RMS_dat0$T2 - baseT)/12
RMS_dat0$T3 <- (RMS_dat0$T3 - baseT)/12
RMS_dat0$T4 <- (RMS_dat0$T4 - baseT)/12
RMS_dat0$T5 <- (RMS_dat0$T5 - baseT)/12
RMS_dat0$T6 <- (RMS_dat0$T6 - baseT)/12
RMS_dat0$T7 <- (RMS_dat0$T7 - baseT)/12
RMS_dat0$T8 <- (RMS_dat0$T8 - baseT)/12
RMS_dat0$T9 <- (RMS_dat0$T9 - baseT)/12
# Standardize time-invariant covariates (TICs)
## ex1 is standardized growth TIC in models
RMS_dat0$ex1 <- scale(RMS_dat0$Approach_to_Learning)
# Standardize time-varying covariate (TVC)
BL_mean <- mean(RMS_dat0[, "R1"])
BL_var <- var(RMS_dat0[, "R1"])
RMS_dat0$Rs1 <- (RMS_dat0$R1 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs2 <- (RMS_dat0$R2 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs3 <- (RMS_dat0$R3 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs4 <- (RMS_dat0$R4 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs5 <- (RMS_dat0$R5 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs6 <- (RMS_dat0$R6 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs7 <- (RMS_dat0$R7 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs8 <- (RMS_dat0$R8 - BL_mean)/sqrt(BL_var)
RMS_dat0$Rs9 <- (RMS_dat0$R9 - BL_mean)/sqrt(BL_var)
xstarts <- mean(baseT)

Example 1: This example includes two models. Model 1 is a full bilinear spline LGCM with a TVC to examine the influence of baseline teacher-reported approach to learning and the development in reading ability on the development of mathematics ability. It also includes a visualization showcasing the growth status of mathematics ability. Model 2 is a full bilinear spline LGCM with a decomposed TVC (interval-specific slopes) to examine the influence of baseline teacher-reported approach to learning and the development in reading ability on the development of mathematics ability. P values and Wald confidence intervals of all parameters are provided. It also includes a visualization showcasing the growth status of mathematics ability.

set.seed(20191029)
Math_TVC_BLS_f <- getTVCmodel(
  dat = RMS_dat0, t_var = "T", y_var = "M", curveFun = "BLS", intrinsic = TRUE, 
  records = 1:9, y_model = "LGCM", TVC = "Rs", decompose = 0, growth_TIC = "ex1", 
  res_scale = 0.1, tries = 10
  ) 
paraBLS_TVC.f <- c(
  "Y_alpha0", "Y_alpha1", "Y_alpha2", "Y_alphag", 
  paste0("Y_psi", c("00", "01", "02", "0g", "11", "12", "1g", "22", "2g", "gg")), 
  "Y_residuals", "X_mueta0", "X_mueta1", paste0("X_psi", c("00", "01", "11")), 
  paste0("X_rel_rate", 2:8), paste0("X_abs_rate", 1:8), "X_residuals",
  paste0("betaTIC", c(0:2, "g")), paste0("betaTVC", c(0:2, "g")), "muTIC", "phiTIC", 
  "Y_mueta0", "Y_mueta1", "Y_mueta2", "Y_mu_knot", "covBL", "kappa", "Cov_XYres"
  )
set.seed(20191029)
Math_TVCslp_BLS_f <- getTVCmodel(
  dat = RMS_dat0, t_var = "T", y_var = "M", curveFun = "BLS", intrinsic = TRUE, 
  records = 1:9, y_model = "LGCM", TVC = "Rs", decompose = 1, growth_TIC = "ex1", 
  res_scale = c(0.1, 0.1), res_cor = 0.3, tries = 10, paramOut = TRUE, 
  names = paraBLS_TVC.f
  ) 

getEstimateStats(est_in = Math_TVCslp_BLS_f@Estimates, CI_type = "Wald")
Figure1 <- getFigure(
  model = Math_TVC_BLS_f@mxOutput, sub_Model = "TVC", y_var = "M", curveFun = "BLS", 
  y_model = "LGCM", t_var = "T", records = 1:9, xstarts = xstarts, xlab = "Year",
  outcome = "Mathematics"
)
show(Figure1)
Figure2 <- getFigure(
  model = Math_TVCslp_BLS_f@mxOutput, sub_Model = "TVC", y_var = "M", curveFun = "BLS", 
  y_model = "LGCM", t_var = "T", records = 1:9, xstarts = xstarts, xlab = "Year",
  outcome = "Mathematics"
)
show(Figure2)

A comparison between Figure 1 and Figure 2 demonstrates that incorporating a TVC directly results in underestimation of the growth factor means.

Example 2: Fit reduced bilinear spline LGCMs with a decomposed TVC (interval-specific slopes, interval-specific changes, and change from baseline) to examine the influence of baseline teacher-reported approach to learning and the development in reading ability on the development of mathematics ability. It also includes a visualization showcasing the growth status of mathematics ability.

paraBLS_TVC.r <- c(
  "Y_alpha0", "Y_alpha1", "Y_alpha2", "Y_knot", 
  paste0("Y_psi", c("00", "01", "02", "11", "12", "22")), "Y_residuals",
  "X_mueta0", "X_mueta1", paste0("X_psi", c("00", "01", "11")), 
  paste0("X_rel_rate", 2:8), paste0("X_abs_rate", 1:8), "X_residuals",
  paste0("betaTIC", 0:2), paste0("betaTVC", 0:2), "muTIC", "phiTIC", 
  "Y_mueta0", "Y_mueta1", "Y_mueta2", "covBL", "kappa", "Cov_XYres"
  )
set.seed(20191029)
Math_TVCslp_BLS_r <- getTVCmodel(
  dat = RMS_dat0, t_var = "T", y_var = "M", curveFun = "BLS", intrinsic = FALSE,
  records = 1:9, y_model = "LGCM", TVC = "R", decompose = 1, growth_TIC = "ex1", 
  res_scale = c(0.1, 0.1), res_cor = 0.3, tries = 10,  paramOut = TRUE, 
  names = paraBLS_TVC.r)    
set.seed(20191029)
Math_TVCchg_BLS_r <- getTVCmodel(
  dat = RMS_dat0, t_var = "T", y_var = "M", curveFun = "BLS", intrinsic = FALSE,
  records = 1:9, y_model = "LGCM", TVC = "R", decompose = 2, growth_TIC = "ex1", 
  res_scale = c(0.1, 0.1), res_cor = 0.3, tries = 10,  paramOut = TRUE, 
  names = paraBLS_TVC.r)    
set.seed(20191029)
Math_TVCchgBL_BLS_r <- getTVCmodel(
  dat = RMS_dat0, t_var = "T", y_var = "M", curveFun = "BLS", intrinsic = FALSE,
  records = 1:9, y_model = "LGCM", TVC = "R", decompose = 3, growth_TIC = "ex1", 
  res_scale = c(0.1, 0.1), res_cor = 0.3, tries = 10,  paramOut = TRUE, 
  names = paraBLS_TVC.r)    

Figure3 <- getFigure(
  model = Math_TVCslp_BLS_r@mxOutput, sub_Model = "TVC", y_var = "M", curveFun = "BLS", 
  y_model = "LGCM", t_var = "T", records = 1:9, xstarts = xstarts, xlab = "Year",
  outcome = "Mathematics"
)
show(Figure3)
Figure4 <- getFigure(
  model = Math_TVCchg_BLS_r@mxOutput, sub_Model = "TVC", y_var = "M", curveFun = "BLS", 
  y_model = "LGCM", t_var = "T", records = 1:9, xstarts = xstarts, xlab = "Year",
  outcome = "Mathematics"
)
show(Figure4)
Figure5 <- getFigure(
  model = Math_TVCchgBL_BLS_r@mxOutput, sub_Model = "TVC", y_var = "M", curveFun = "BLS", 
  y_model = "LGCM", t_var = "T", records = 1:9, xstarts = xstarts, xlab = "Year",
  outcome = "Mathematics"
)
show(Figure5)

nlpsem documentation built on Sept. 13, 2023, 1:06 a.m.