dae (version 3.0-32)

projector: Create projectors

Description

The class "projector" is the subclass of the class "matrix" in which matrices are square, symmetric and idempotent.

The function projector tests whether a matrix satisfies these criteria and if it does creates a "projector" object, computing the projector's degrees of freedom and adding them to the object.

Usage

projector(Q)

Arguments

Q

The matrix to be made into a projector.

Value

An object of Class "projector" that consists of a square, summetric, idempotent matrix and degrees of freedom (rank) of the matrix.

Details

In checking that the matrix is square, symmetric and idempotent, the equality of the matrix with either its transpose or square is tested. In this, a difference in elements is considered to be zero if it is less than daeTolerance, which is initially set to .Machine$double.eps ^ 0.5 (about 1.5E-08). The function set.daeTolerance can be used to change daeTolerance.

See Also

degfree, correct.degfree in package dae.

projector for further information about this class.

Examples

# NOT RUN {
## set up a 2 x 2 mean operator that takes the mean of a vector of 2 values
m <- matrix(rep(0.5,4), nrow=2)

## create an object of class projector
proj.m <- projector(m)

## check that it is a valid projector
is.projector(proj.m)
# }