Dear Raul,
The difference between the two models is
... Tr.dob Tr.lw ...
vs
... lin(dob) lin(lw)
where dob and lw are both covariates.
Since dob and lw are covariates, the lin() function does nothing.
So the second model is actually
... dob lw ...
So the difference is that the first model has a dob regression
and an lw regression for both traits
whereas the second model has the same regressions for the traits.
Arthur
> From: ponzoni.raul@wpo.pi.sa.gov.au
> Date: Thu, 27 May 1999 12:40:35 +0930
> To: gilmoua@ornsun.agric.nsw.gov.au
> Subject: Covariance analyses
>
> Arthur,
> I sent the message below to the users' ASREML group, but did not get a reply.
> Regards,
> Raul
>
>
********************************************************************************
************
>
> A PhD student is analysing some sheep data. The traits in question are two
> scrotal a circumferences. She would like to fit age (coded as dob) and live
> weight as covariates. The two options below work and give 'reasonable'
> results. The first option is as shown in an example in the ASREML Manual.
> The second option uses lin( ). The two options give very similar results, but
> they are not identical. Why is this so? Is there a prefered option for this
sort of
> situation?
>
>
> First option
>
> Animal Model
> animal !P
> sire
> dam
> year 4 !I
> stud 4
> aod 4 !I
> tob_r 5 !I
> dob 1
> lw 1
> sc5
> sc10
> sc16
>
> c:\asr\ped5.dat
> c:\asr\ped5.dat
>
> sc5 sc10 ~ Trait Tr.year Tr.stud Tr.aod Tr.tob_r Tr.dob Tr.lw !r Tr.animal
> 1 2 1 # 1 set of resid, 2 dim anim.trait, G str tr.animal
> 0 # use all records
> 2 0 US 8.11 3.98 8.79 # no. of traits, records sorted,US, residual ervar1
erco12
> ervar2
>
> Tr.animal 2 # 2 dim struct, always 2
> 2 0 US 0.90 0.27 0.69 # 2 traits, sorted, US, animal var1 cov12 var2
> 0 # use all records
>
>
>
> Second option
>
> Animal Model
> animal !P
> sire
> dam
> year 4 !I
> stud 4
> aod 4 !I
> tob_r 5 !I
> dob 1
> lw 1
> sc5
> sc10
> sc16
>
> c:\asr\ped5.dat
> c:\asr\ped5.dat
>
> sc5 sc10 ~ Trait Tr.year Tr.stud Tr.aod Tr.tob_r lin(dob) lin(lw) !r Tr.animal
> 1 2 1 # 1 set of resid, 2 dim anim.trait, G str tr.animal
> 0 # use all records
> 2 0 US 8.11 3.98 8.79 # no. of traits, records sorted,US, residual ervar1
erco12
> ervar2
>
> Tr.animal 2 # 2 dim struct, always 2
> 2 0 US 0.90 0.27 0.69 # 2 traits, sorted, US, animal var1 cov12 var2
> 0 # use all records
>
>
> Thanks for your help,
>
> Dr Raul W. Ponzoni
> Principal Research Scientist (Livestock Genetics)
> South Australian Research and Development Institute
> G P O Box 397
> Adelaide SA
> AUSTRALIA 5001
>
> Telephone 61 8 8303 9410
> Facsimile 61 8 8303 9424
>
> E-mail ponzoni.raul@pi.sa.gov.au
>
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Arthur Gilmour PhD mailto:Arthur.Gilmour@agric.nsw.gov.au
Senior Research Scientist (Biometrics) fax: <61> 2 6391 3899
NSW Agriculture <61> 2 6391 3922
Orange Agricultural Institute telephone work: <61> 2 6391 3815
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