Re: [Fwd: asreml]

Dear

re:

I'm fitting a model with an animal effect and a permanent environment
effect. Individuals are spread over two time periods and I want to
test whether a model with time specific animal and PE effects is
better than a model where both periods are treated equally. For
univariate models this is fine:

T1 ~ mu time !r at(time,1).animal at(time,2).animal at(time,
1).identity at(time,2).identity

versus

T1 ~ mu time !r animal identity

Comments:

1. The univariate models reported assume repeated measures
2. The comparison across time assumes no genetic links between times.
Otherwise,
it would be better to include a correlation.
3. Also, if you are allowing different genetic and PE variances, it would
be better
to also allow different residual variances.

Consequently, my version of the first model might end up being

T1 ~ mu time !r time.animal time.identity !uni(time,2) !GU
0 0 2
time.animal 2
time 0 US !GP # assuming genetic links, else DIAG
.1 .01 .1
animal 0 AINV

time.identity 2
time 0 DIAG .1 .1 !GP
identity

===========================
You further wrote
If I fit a multivariate model either the animal or the PE effects are
flagged as singular depending on which order the terms are fitted. I
am confident that these parameters can be estimated from the data
because a) all (3) traits have the same pattern of missing data so if
the univariate model is idenitifiable the multivariate model should
be and b) I can fit a multivariate model for each time period
separately by generating two data sets and all model parameters are
estimated. One potential issue is that some individuals are present
in both time periods, but I can't see why this should cause
singularities.

The most likely cause is that ASReml may not associate the A inverse with
the Tr.time.animal term
when written as a G structure unless it is explicity declared in the
appropriate fashion (see eaxample above).

My attempt at your model is

T1 T2 T3 ~ Trait time Tr.time !r Tr.time.animal Tr.time.identity
2 2 2
zzz # Insert number of records at time 1 after sorting the data
Trait 0 US !GP
6*0

zzz # Insert number of records at time 2 after sorting the data
Trait 0 US !GP
6*0

Tr.time.animal 3
Trait 0 US !GP
6*0
time 0 CORUH !GPPF
.1 1 1
animal 0 AINV

Tr.time.identity 3
Trait 0 US !GP
6*0
time 0 CORUH !GPPF
.1 1 1
identity

This is a fairly sophisticated model, so may need better starting values
than I've given.
If you only have a little bit of data, it may be too sophisticated for
your data.
But, according to my understanding of your email, this is what you are
moving towards.

May you know Jesus Christ and His blessing in 2007,

Arthur Gilmour, His servant .

PS My Mixed Model Regression Mapping paper is now available at
http://dx.doi.org/10.1016/j.csda.2006.12.031

Profile: http://www.dpi.nsw.gov.au/reader/17263
Personal website: http://www.cargovale.com.au/

mailto:Arthur.Gilmour_at_dpi.nsw.gov.au, arthur_at_cargovale.com.au
Principal Research Scientist (Biometrics)
NSW Department of Primary Industries
Orange Agricultural Institute, Forest Rd, ORANGE, 2800, AUSTRALIA

fax: 02 6391 3899; 02 6391 3922 Australia +61
telephone work: 02 6391 3815; home: 02 6364 3288; mobile: 0438 251 426

ASREML 2 is now available from http://www.VSNi.co.uk/products/asreml
The ASReml discussion group is at ASREML-L_at_dpi.nsw.gov.au
To join it, mailto:arthur.gilmour_at_dpi.nsw.gov.au
Cookbook: http://uncronopio.org/ASReml

Proposed travel:
ASReml workshop (Forestry) 16-18 April Tasmania
Biom Brch meet 2-4 May
ASReml workshop (Animal Breeding) 8-26 May South Africa
AAABG 24-26 September Armidale
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Received on Sat Feb 06 2007 - 14:08:32 EST