[R-sig-ME] Are BLUP from two different random factors independant ?

[LASSALVY Stephane]

Hello all,
I am encountering a question related to linear combination of the estimations of random effects with the Asreml-R package. I am considering the problem of getting the sum of two BLUP. I only want to make the sum of two random effects.

My team and I, we are modelling over the years and over networks field trials data. The number of years which we use for an analysis is usually 2 and the number of networks is 3.

The model which we use is :
Yield = intercept + year + network + year x network + year x network x trial + [[variety]] + [[variety x network]] + [[variety x year x network]] + [[variety x year x network x trial]] + [[error term ]]

Year, network, year x network are fixed effects. The terms between brackets [[ ]] are random terms so we can compute BLUP.

We get the estimation of random terms for single random terms with the summary.asreml command with the all = TRUE option.


  1.  Would you know a mean to compute the sum of two random terms estimations ? We are mostly interested in computing the sum of a BLUP "variety x network" and the related BLUPs for the "variety x year x network" term to get the estimation of the variety x network interaction for each year of trial. Computing the sum of the estimations is not so difficult, but I am not sure that we will be able to compute the standard error for such a sum. Therefore, if a function like predict is able to compute this sum, it would be a very good news for us.



  1.  In case I would have to do the calculation by myself, can I consider that, as  the random factors [[variety x network]]  and  [[variety x year x network]] are independent, for a given variety, BLUP(variety x network) and BLUP(variety x year x network) ?

Best regards,
Stephane

St�phane LASSALVY
GEVES La Valette
711, rue Jean-Fran�ois Breton
F-34090 Montpellier
T�l. +33 (0)4 67 04 35 81
Email : stephane.lassalvy using geves.fr<mailto:contact using geves.fr>


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