[.pdMat                 package:nlme                 R Documentation

Subscript a pdMat Object

Description:

     This method function extracts sub-matrices from the
     positive-definite matrix represented by 'x'.

Usage:

     ## S3 method for class 'pdMat':
     x[i, j, drop = TRUE]
     ## S3 replacement method for class 'pdMat':
     x[i, j] <- value

Arguments:

       x: an object inheriting from class 'pdMat' representing a
          positive-definite matrix.

    i, j: optional subscripts applying respectively to the rows and
          columns of the positive-definite matrix represented by
          'object'. When 'i' ('j') is omitted, all rows (columns) are
          extracted.

    drop: a logical value. If 'TRUE', single rows or columns are
          converted to vectors. If 'FALSE' the returned value retains
          its matrix representation.

   value: a vector, or matrix, with the replacement values for the
          relevant piece of the matrix represented by 'x'.

Value:

     if 'i' and 'j' are identical, the returned value will be 'pdMat'
     object with the same class as 'x'. Otherwise, the returned value
     will be a matrix. In the case a single row (or column) is
     selected, the returned value may be converted to a vector,
     according to the rules above.

Author(s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

See Also:

     '[', 'pdMat'

Examples:

     pd1 <- pdSymm(diag(3))
     pd1[1, , drop = FALSE]
     pd1[1:2, 1:2] <- 3 * diag(2)

