SA_step2 {phantSEM}

Step 2 of sensitivity analysis function

Description

SA_step2() is used to assign values to the phantom covariances. There are three options for assigning values to the phantom covariances: 1. Fix phantom covariance to a numeric value (i.e., 0 or 1), 2. Fix phantom covariance to be equal to another covariance, or 3. Test different values for the phantom covariance.

Usage

SA_step2(phantom_assignment, step1)

Arguments

phantom_assignment

A list of all phantom parameter names (copied from SA_step1() output) which assigns them to be equal to ONE of the following: 1) an observed parameter name, 2) a single numeric value, 3) a sequence of values, or 4) another phantom variable that has been set equal to 1-3.

step1

The output object created in SA_step1()

Value

A list containing test covariance matrices that the phantom model will be fit to.

Examples

covmatrix <- matrix(c(
  0.25, 0.95, 0.43,
  0.95, 8.87, 2.66,
  0.43, 2.66, 10.86
), nrow = 3, byrow = TRUE)
colnames(covmatrix) <- c("X", "M2", "Y2")

# lavann syntax for observed model
observed <- " M2 ~ X
             Y2 ~ M2+X "

# lavaan output
obs_output <- lavaan::sem(model = observed, sample.cov = covmatrix, sample.nobs = 200)

# lavaan syntax for phantom variable model
phantom <- " M2 ~ M1 + Y1 + a*X
               Y2 ~ M1 + Y1 + b*M2 + cp*X "

Step1 <- SA_step1(
  lavoutput = obs_output,
  mod_obs = observed,
  mod_phant = phantom
)

phantom_assignment <- list(
  "CovM1X" = 0,
  "CovY1M1" = "CovY2M2",
  "CovY1X" = 0,
  "VarM1" = 1,
  "VarY1" = 1,
  "CovM1M2" = seq(0, .6, .1),
  "CovY1Y2" = "CovM1M2",
  "CovY1M2" = seq(-.6, .6, .1),
  "CovM1Y2" = "CovY1M2"
)
Step2 <- SA_step2(
  phantom_assignment = phantom_assignment,
  step1 = Step1
)