getclf returns a function proportional to twice the negative
log likelihood function for multivariate normal data with missing
values. This is a private function used in
A data frame sorted so that records with identical patterns of missingness are grouped together.
An integer vector specifying the number of records in each block of data with identical patterns of missingness.
The argument of the returned function is the vector of parameters. The parameterization is: mean vector first, followed by the log of the diagonal elements of the inverse of the Cholesky factor, and then the elements of the inverse of the Cholesky factor above the main diagonal. These off-diagonal elements are ordered by column (left to right), and then by row within column (top to bottom).
A function proportional to twice the negative log likelihood of the parameters given the data.
Little, R. J. A., and Rubin, D. B. (1987) Statistical Analysis with Missing Data. New York: Wiley.