dySEM: Dyadic Structural Equation Modeling

Documented in scriptUni

#' A Function That Writes, Saves, and Exports Syntax for
#' Fitting Unidimensional Dyadic Factor Models
#'
#' This function takes the outputted object from scrapeVarCross()
#' and automatically writes, returns, and exports (`.txt`) `lavaan` syntax
#' for specifying dyadic configural, loading, intercept, and residual invariant
#' one-factor models.
#'
#' @param dvn Input dvn list from `scrapeVarCross()`.
#' @param scaleset Input character to specify how to set the scale of the latent variable. Default is
#'  `"FF"` (fixed-factor; see Details for rationale), but user can specify `"MV"` (Marker Variable).
#' @param lvname Input character to (arbitrarily) name the latent variable in `lavaan` syntax.
#' @param constr_dy_meas Input character vector detailing which measurement model parameters to constrain across dyad members.
#' @param constr_dy_struct Input character vector detailing which structural model parameters to constrain across dyad members.
#'  **Note**: Within the context of `scriptUni()`, `constr_dy_struct` is **irrelevant**, as the unidimensional dyadic factor model
#'  assumes a single latent variable shared by both partners, leaving no structural parameters to constrain across the modeled dyad members.
#'  For consistency with other scripter functions, `constr_dy_struct` is included as an argument,
#'  but defaults to `"none"`.
#' @param writeTo A character string specifying a directory path to where a `.txt` file of the resulting `lavaan` script should be written.
#'  If set to `“.”`, the `.txt` file will be written to the current working directory.
#'  The default is `NULL`, and examples use a temporary directory created by `tempdir()`.
#' @param fileName A character string specifying a desired base name for the `.txt` output file.
#'  The default is `NULL`. The specified name will be automatically appended with the `.txt` file extension.
#'  If a file with the same name already exists in the user's chosen directory, it will be overwritten.
#' @return Character object of `lavaan` script that can be passed immediately to
#'  `lavaan` functions.
#'
#' @details
#' * Users do not need to modify `constr_dy_struct` when using `scriptUni()`.
#' * By default, many `dySEM::` functions (including `scriptUni()`) default to
#'    a fixed-factor method of scale-setting, whereby the latent variance of
#'    a given factor is constrained to 1 for both partners in the configurally invariant
#'    model, and then one of these variances is freely estimated in subsequent
#'    models of the invariance testing sequence.
#'    We have selected this default for two reasons:
#'    (1) the selection of a marker-variable is usually arbitrary,
#'    yet can have a large influence on the estimation and testing of of structural parameters
#'    (see https://stats.stackexchange.com/questions/402133/in-cfa-does-it-matter-which-factor-loading-is-set-to-1/402732#402732);
#'    and (2) the selection of a non-invariant marker-variable
#'    can have disastrous down-stream consequences for the identification of
#'    non-invariant measurement parameters, following a the rejection of an omnibus
#'    invariance constraint set (see Lee, Preacher, & Little, 2011).
#'
#' @seealso \code{\link{scrapeVarCross}} which this function relies on.
#' @family uni-construct script-writing functions
#' @export
#'
#' @examples
#'
#' dvn <- scrapeVarCross(
#'   commitmentQ,
#'   x_order = "spi",
#'   x_stem = "sat.g",
#'   x_delim1 = ".",
#'   x_delim2="_",
#'   distinguish_1="1",
#'   distinguish_2="2"
#'   )
#'
#' sat.resids.script <- scriptUni(
#'   dvn,
#'   scaleset = "FF",
#'   lvname = "Sat",
#'   constr_dy_meas = c("loadings", "intercepts", "residuals"),
#'   constr_dy_struct = "none",
#'   writeTo = tempdir(),
#'   fileName = "dUni_residual"
#'   )
#'
#' sat.ints.script <- scriptUni(
#'   dvn,
#'   scaleset = "FF",
#'   lvname = "Sat",
#'   constr_dy_meas = c("loadings", "intercepts"),
#'   constr_dy_struct = "none",
#'   writeTo = tempdir(),
#'   fileName = "dUni_intercept"
#'   )
#'
#' sat.loads.script <- scriptUni(
#'   dvn,
#'   scaleset = "FF",
#'   lvname = "Sat",
#'   constr_dy_meas = c("loadings"),
#'   constr_dy_struct = "none",
#'   writeTo = tempdir(),
#'   fileName = "dUni_loading"
#'   )
#'
#' sat.config.script <- scriptUni(
#'   dvn,
#'   scaleset = "FF",
#'   lvname = "Sat",
#'   constr_dy_meas = "none",
#'   constr_dy_struct = "none",
#'   writeTo = tempdir(),
#'   fileName = "dUni_configural"
#'   )
#'
scriptUni <- function(
    dvn,
    scaleset = "FF",
    lvname = "X",
    constr_dy_meas = c("loadings", "intercepts", "residuals"),
    constr_dy_struct = "none", #Users do not need to modify `constr_dy_struct` when using `scriptUni()`.
    writeTo = NULL,
    fileName = NULL
    ){

  #check for valid inputs
  if(length(dvn)!=6){
    stop("You must supply a dvn object containing information for only X [i.e., your target LV]")
  }

  if(!scaleset %in% c("FF", "MV")){
    stop("scaleset must be either 'FF' (fixed-factor) or 'MV' (marker variable)")
  }

  if(!any(constr_dy_meas %in% c("loadings", "intercepts", "residuals", "none"))){
    stop("constr_dy_meas must be a character vector containing any combination of 'loadings', 'intercepts', 'residuals', or 'none'")
  }

  if(!any(constr_dy_struct %in% c("none"))){
    stop("constr_dy_struct is not applicable to `scriptUni()`.
          Please leave it as the default value: 'none'.")
  }

  #fixed factor
  if(scaleset == "FF"){

    #loadings
    if(any(constr_dy_meas == "loadings")){
      xloadsg <- loads(
        dvn,
        lvar = "X",
        lvname,
        partner = "g",
        type = "equated"
      )
    }
    else {
      xloadsg <- loads(
        dvn,
        lvar = "X",
        lvname,
        partner = "g",
        type = "free"
      )
    }

    #intercepts
    if(any(constr_dy_meas == "intercepts")){
      xints1 <- intercepts(
        dvn,
        lvar = "X",
        partner = "1",
        type = "equated"
      )
      xints2 <- intercepts(
        dvn,
        lvar = "X",
        partner = "2",
        type = "equated"
      )
    }
    else {
      xints1 <- intercepts(
        dvn,
        lvar = "X",
        partner = "1",
        type = "free"
      )
      xints2 <- intercepts(
        dvn,
        lvar = "X",
        partner = "2",
        type = "free"
      )
    }

    #residuals
    if(any(constr_dy_meas == "residuals")){
      xres1 <- resids(
        dvn,
        lvar = "X",
        partner = "1",
        type = "equated"
      )
      xres2 <- resids(
        dvn,
        lvar = "X",
        partner = "2",
        type = "equated"
      )
    }
    else {
      xres1 <- resids(
        dvn,
        lvar = "X",
        partner = "1",
        type = "free"
      )
      xres2 <- resids(
        dvn,
        lvar = "X",
        partner = "2",
        type = "free"
      )
    }

    #correlated residuals
    xcoresids <- coresids(
      dvn,
      lvar = "X",
      type = "free"
    )

    #latent variances
    xvarg <- lvars(
      dvn,
      lvar = "X",
      lvname,
      partner = "g",
      type = "fixed"
    )

    #latent means
    xmeang <- lmeans(
      dvn,
      lvar = "X",
      lvname,
      partner = "g",
      type = "fixed"
    )

    #Script Creation Syntax
    script <- sprintf(
      "#Measurement Model\n\n#Loadings\n%s\n\n#Intercepts\n%s\n\n%s\n\n#Residual Variances\n%s\n\n%s\n\n#Residual Covariances\n%s\n\n#Structural Model\n\n#Latent (Co)Variances\n%s\n\n#Latent Means\n%s",
      xloadsg,
      xints1, xints2,
      xres1, xres2, xcoresids,
      xvarg,
      xmeang
    )

  }

  #marker variable
  if(scaleset == "MV"){

    #loadings
    if(any(constr_dy_meas == "loadings")){
      xloadsg <- loads(
        dvn,
        lvar = "X",
        lvname,
        partner = "g",
        type = "equated_mv"
      )
    }
    else {
      xloadsg <- loads(
        dvn,
        lvar = "X",
        lvname,
        partner = "g",
        type = "fixed"
      )
    }

    #intercepts
    if(any(constr_dy_meas == "intercepts")){
      xints1 <- intercepts(
        dvn,
        lvar = "X",
        partner = "1",
        type = "equated_mv"
      )
      xints2 <- intercepts(
        dvn,
        lvar = "X",
        partner = "2",
        type = "equated" #keep as "equated" in scriptUni
      )
    }
    else {
      xints1 <- intercepts(
        dvn,
        lvar = "X",
        partner = "1",
        type = "fixed"
      )
      xints2 <- intercepts(
        dvn,
        lvar = "X",
        partner = "2",
        type = "free" #keep as "free" in scriptUni
      )
    }

    #residuals
    if(any(constr_dy_meas == "residuals")){
      xres1 <- resids(
        dvn,
        lvar = "X",
        partner = "1",
        type = "equated"
      )
      xres2 <- resids(
        dvn,
        lvar = "X",
        partner = "2",
        type = "equated"
      )
    }
    else {
      xres1 <- resids(
        dvn,
        lvar = "X",
        partner = "1",
        type = "free"
      )
      xres2 <- resids(
        dvn,
        lvar = "X",
        partner = "2",
        type = "free"
      )
    }

    #correlated residuals
    xcoresids <- coresids(
      dvn,
      lvar = "X",
      type = "free"
    )

    #latent variances
    xvarg <- lvars(
      dvn,
      lvar = "X",
      lvname,
      partner = "g",
      type = "free"
    )

    #latent means
    xmeang <- lmeans(
      dvn,
      lvar = "X",
      lvname,
      partner = "g",
      type = "free"
    )

    #Script Creation Syntax
    script <- sprintf(
      "#Measurement Model\n\n#Loadings\n%s\n\n#Intercepts\n%s\n\n%s\n\n#Residual Variances\n%s\n\n%s\n\n#Residual Covariances\n%s\n\n#Structural Model\n\n#Latent (Co)Variances\n%s\n\n#Latent Means\n%s",
      xloadsg,
      xints1, xints2,
      xres1, xres2, xcoresids,
      xvarg,
      xmeang
    )

  }


  #Write script to file if requested
  if(!is.null(writeTo) | !is.null(fileName) ){
    #if there is a path or file name,
    #check for valid input,
    #and if valid, write script

    # checking for valid directory path and fileName
    if (!is.character(writeTo)){
      stop("The `writeout` argument must be a character string. \n Use writeTo = '.' to save script in the current working directory, for example.")
    }
    if (!dir.exists(writeTo)){
      stop("The specified directory does not exist. \n Use writeTo = '.' to save script in the current working directory, for example.")
    }
    if (!is.character(fileName)){
      stop("The `fileName` argument must be a character string.")
    }

    #write file
    cat(script, "\n",
        file = sprintf("%s/%s.txt",
                       writeTo,
                       fileName))

    return(script)
  }
  else if(is.null(writeTo) & is.null(fileName)){
    #otherwise just return script
    return(script)
  }

}