Extended Factor Analytic model
xfa(f,k) and xfak(f)
xfa(f,k)
Factor
analytic models are available in
three forms in ASReml: FAk,
FACVk
and XFAk
where k is the number of factors.
The XFAk form is
a sparse formulation that requires an extra k levels to be
inserted into the mixed model equations for the k
factors. This is achieved by the xfa(f,k) model function
which defines a design matrix based on the design matrix for f
augmented with k columns of
zeros for the k factors.
There are two forms of the xfa model function.
The original form was
xfa(f,k)
and simply modifies the design matrix for factor f
by appending k more levels. With this form, the XFAk
variance structure must be specified separately.
The new form is
xfak(f)
and this associates the XFAk variance structure with the term
as well as creating the extra k columns (to hold the k factors).
See Also
Return to index