| is_estimable {doBy} | R Documentation |
Determines if contrasts are estimable, that is, if the contrasts can be written as a linear function of the data.
is_estimable(K, null.basis)
K |
A matrix. |
null.basis |
A basis for a null space (can be found with |
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.
A logical vector.
Søren Højsgaard, sorenh@math.aau.dk
http://web.mit.edu/18.06/www/Essays/newpaper_ver3.pdf
## TO BE WRITTEN