mxSave: Save End State to Checkpoint File

Description

The function saves the last state of a model to a checkpoint file.

Usage

mxSave(model, chkpt.directory = ".", chkpt.prefix = "")

Arguments

model

MxModel object to be loaded.

chkpt.directory

character. Directory where the checkpoint file is located.

chkpt.prefix

character. Prefix of the checkpoint file.

Details

In general, the arguments chkpt.directory and chkpt.prefix should be identical to the mxOption: Checkpoint Directory and Checkpoint Prefix that were specificed on the model before execution.

Alternatively, the checkpoint file can be manually loaded as a data.frame in R. Use read.table with the options header=TRUE, sep="", stringsAsFactors=FALSE, check.names=FALSE.

Returns a logical indicating the succes of writing the checkpoint file to the checkpoint directory.

The OpenMx User's guide can be found at http://openmx.psyc.virginia.edu/documentation.

library(OpenMx)

# Simulate some data

x=rnorm(1000, mean=0, sd=1) y= 0.5*x + rnorm(1000, mean=0, sd=1) tmpFrame <- data.frame(x, y) tmpNames <- names(tmpFrame)

# Create a model that includes an expected covariance matrix, # an expectation function, a fit function, and an observed covariance matrix

data <- mxData(cov(tmpFrame), type="cov", numObs = 1000) expCov <- mxMatrix(type="Symm", nrow=2, ncol=2, values=c(.2,.1,.2), free=TRUE, name="expCov") expFunction <- mxExpectationNormal(covariance="expCov", dimnames=tmpNames) fitFunction <- mxFitFunctionML() testModel <- mxModel(model="testModel", expCov, data, expFunction, fitFunction)

#Use mxRun to optimize the free parameters in the expected covariance matrix modelOut <- mxRun(testModel) modelOut$expCov

# Save the ending state of modelOut in a checkpoint file mxSave(modelOut)

# Restore the saved model from the checkpoint file modelSaved <- mxRestore(testModel) modelSaved$expCov

# Imagine how much time you saved by not having to re-run the # model that took hours or days to run.