Wilmik and random regression

From: Bruce Southey <southey_at_UIUC.EDU>
Date: Mon, 10 Oct 2005 08:03:40 -0500

Hi,
Wilmik's curve is not random regression but rather a nonlinear function like
other functions such as Wood's. Apart from the nonlinear generalized linear
models, these models can not be fitted as such in ASREML. In the case of Wilmik
if the c parameter is treated as known then it becomes a simple linear model and
can be fitted. However, this is usually rather stupid because biases the
results. Also if you knew this parameter then there is no need to fit the model.

Regards
Bruce

---- Original message ----
>Date: Thu, 6 Oct 2005 12:54:23 +0200
>From: Nicola Macciotta <macciott_at_UNISS.IT>
>To: ASREML-L_at_AGRIC.NSW.GOV.AU
>
>Dear ASREML users,
>I am trying to run a random regression model for milk yield where I would
>like to test for modeling individual random deviations wioh different
>functions, some of them are not implemented in the ASREML software. For
>example, the function proposed by Wilmink (1987, Liv. Prod. Sci.)
>
>Ydim= a + be-kdim + cdim
>
>where dim are the days in milk. The function can be linearised by setting k
>to a fixed value (0.1 for example).
>
>So the model I want to use has three terms
>
>a the intercept
>
>b that actually is (be-0.1dim )
>
>
>c x dim
>
>So my question is: how can I put this function as random within animal?
>Could be this the correct syntax of the random part of the model?
>
>r! a.animal b.animal dim.animal
>
>
>and how can I get the (co)variance matrix of coefficients?
>
>
>Thank you very much for your help
>
>Nicol˛
>
>Nicol˛ P.P. Macciotta
>Dipartimento di Scienze Zootecniche
>UniversitÓ degli Studi di Sassari
>Via De Nicola, 9
> 07100 Sassari, Italia
>tel 39.079.229298 fax 39.079.229302
>e-mail macciott_at_uniss.it
Received on Sun Oct 10 2005 - 08:03:40 EST

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