pdFactor.pdInd: Factor of a pdInd object.
In gmonette/Tcells: Fits Tcell dynamic models with mixed models

Description Usage Arguments Details Value Examples

Function to compute the upper triangular factor of a pdInd object representing the factorization of the inverse variance matrix.

1 2	## S3 method for class 'pdInd' pdFactor(object)

object

a 'pdInd' object from which the right-triangular factor of the variance matrix it represents will be extracted

Returns a factor for a right log-Cholesky object for positive-definite inverse variance matrix corresponding to a variance matrix with zero covariances except in the first row and column. i.e. $$ V^-1 = R'R $$ with $R$ a right-triangular matrix.

Then if the upper-diagonal elements of $R$ below the first row are all 0 then the corresponding variance matrix with will have zero covariances except on the first row (and column).

the full right-triangular factor, including zeros in the lower triangle, is returned as a vector in column order