Variance Models
OWN variance model
The OWN variance structure is
a facility whereby users may specify their own variance structure.
This facility requires the user to supply a
program MYOWNGDG that reads the current set of parameters,
forms the G matrix and
a full set of derivative matrices, and writes these to disk.
Before each iteration, ASReml writes the OWN parameters to a file,
runs MYOWNGDG (which it presumes forms the G and derivative
matrix) and then reads the matrices back in. An example of MYOWNGDG.f90
is distributed with ASReml. It duplicates the AR1
and AR2 structures.
The following job fits an AR2 structure using this program.
Example of using the OWN structure
rep
blcol
blrow
variety 25
yield
barley.asd !skip 1 !OWN MYOWN.EXE
yield ~ variety
1 2
10 0 AR1 .1
15 0 OWN2 .2 .1 !TRR
The file written by ASReml has extension .own and looks like
15 2 1
0.6025860D+000.1164403D+00
This file was written by asreml for reading by your
program MYOWNGDG
asreml writes this file, runs your program and then reads
shfown.gdg
which it presumes has the following format:
The first lines should agree with the top of this file
specifying the order of the matrices ( 15)
the number of variance parameters ( 2)
and a control parameter you can specify ( 1).
These are written in (3I5) format. They are followed by
the list of variance parameters written in (6D13.7) format.
Follow this with 3 matrices written in (6D13.7) format.
These are to be each of 120 elements being lower triangle
rowwise of the G matrix and its derivatives with respect
to the parameters in turn.
This file contains details about what is expected in the file
written by your program. The filename used has the same basename as
the job you are running with extension .own for the file
written by ASReml and .gdg for the file your program writes.
The type of the parameters is set with the !T qualifier described below.
The control parameter is set using the !F qualifier.
!F2
applies to OWN models.
With OWN,
the argument of !F
is passed to the MYOWNGDG
program as
an argument the program can access. This is the mechanism that allows
several OWN models to be fitted in a single run.
!Ts
is used to set the type of the parameters.
It is primarily used in conjunction with the OWN structure as ASReml knows
the type in other cases. The valid type codes are as follows:

Code 
Description 
Action with !GP


V  variance  forced positive


G  variance ratio  forced positive


R  correlation 
1 < r < 1


C  covariance 


P  positive correlation
 0 < r < 1


L  loading 

This coding also affects whether the parameter is scaled by
the residual variance in the output.
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