is-estimable: Determines if contrasts are estimable.
In hojsgaard/doBy: Groupwise Statistics, LSmeans, Linear Estimates, Utilities

is-estimable

R Documentation

Determines if contrasts are estimable.

Description

Determines if contrasts are estimable, that is, if the contrasts can be written as a linear function of the data.

Usage

is_estimable(K, null.basis)

Arguments

`K`	A matrix.
`null.basis`	A basis for a null space (can be found with `null_basis()`).

Details

Consider the setting E(Y)=Xb. A linear function of b, say l'b is estimable if and only if there exists an r such that r'X=l' or equivalently l=X'r. Hence l must be in the column space of X', i.e. in the orthogonal complement of the null space of X. Hence, with a basis B for the null space, is_estimable() checks if each row l of the matrix K is perpendicular to each column basis vector in B.