mxData {OpenMx}R Documentation

Function To Create MxData Object


This function creates a new MxData object.


mxData(observed, type, means = NA, numObs = NA)


observed A matrix or data.frame which provides data to the MxData object.
type A character string defining the type of data in the ‘observed’ argument. Must be one of “raw”, “cov”, “cor”, or “sscp”.
means An optional vector of means for use when ‘type’ is “cov”, or “cor”.
numObs The number of observations in the data supplied in the ‘observed’ argument. Required unless ‘type’ equals “raw”.


The mxData function creates MxData objects, which can be used as arguments in MxModel objects. The ‘observed’ argument may take either a data frame or a matrix, which is then described with the ‘type’ argument. Data types describe compatibility and usage with objective functions in MxModel objects. Four different data types are supported:

MxData objects may not be included in MxAlgebra objects or use the mxAlgebraObjective function. If these capabilities are desired, data should be appropriately input or transformed using the mxMatrix and mxAlgebra functions.

While column names are stored in the ‘observed’ slot of MxData objects, these names are not recognized as variable names in MxPath objects. Variable names must be specified using the ‘manifestVars’ argument of the mxModel function prior to use in MxPath objects.

The mxData function does not currently place restrictions on the size, shape, or symmetry of matrices input into the ‘observed’ argument. While it is possible to specify MxData objects as covariance, correlation or sscp matrices that do not have the properties commonly associated with these matrices, failure to correctly specify these matrices will likely lead to problems in model estimation.


Returns a new MxData object.


The OpenMx User's guide can be found at

See Also

MxData for the S4 class created by mxData. matrix and data.frame for objects which may be entered as arguments in the ‘observed’ slot. More information about the OpenMx package may be found here.


#Create a covariance matrix
covMatrix <- matrix( c(0.77642931, 0.39590663, 
    0.39590663, 0.49115615), 
    nrow = 2, ncol = 2, byrow = TRUE)

#Create an MxData object including that covariance matrix
data <- mxData(covMatrix, 'cov', numObs = 100)

model <- mxModel(data) 

[Package OpenMx version 0.1-1 Index]