equivalent of DROP in OpenMx interface

There's been some discussion among the beta testers to support setting a free parameter to a fixed parameter across an entire model, or setting a fixed parameter to a free parameter across an entire model. Here's a function in R that will accomplish the transformation. The 'model argument is a MxModel object. The 'labels' argument is a vector of parameter names. The 'free' argument is either a NA or a single TRUE or FALSE. The 'value' argument is either a NA or a single numeric value. If 'free' is not NA, then all the parameters with name 'labels' will have their free/fixed status changed to 'free'. If 'value' is not NA, then all the parameters with name 'labels' with have their starting values changed to 'value'.

setParameters <- function(model, labels, free = NA, value = NA) {
   if(missing(model) || !is(model, "MxModel")) {
      stop("The 'model' argument must be a MxModel object")
   }
   if(missing(labels) || typeof(labels) != "character") {
      stop("The 'labels' argument must be a vector of characters")
   }
   if(!is.na(free) && (typeof(free) != "logical" || length(free) != 1)) {
      stop("The 'free' argument must be a single boolean value")
   }
   if(!is.na(value) && (!is.numeric(value) || length(value) != 1)) {
      stop("The 'value' argument must be a single numeric value")
   }
   return(setParametersHelper(model, labels, free, value))
}

setParametersHelper <- function(model, labels, free, value) {
   model@matrices <- lapply(model@matrices, setParametersMatrix, labels, free, value)
   model@submodels <- lapply(model@submodels, setParametersHelper, labels, free, value)
   return(model)
}

setParametersMatrix <- function(matrix, labels, free, value) {
   select <- apply(matrix@labels, c(1,2), function(x) {!is.na(x) && x %in% labels})
   if (!is.na(free)) {
      matrix@free[select] <- free
   }
   if (!is.na(value)) {
      matrix@values[select] <- value
   }
   return(matrix)
}