Re: why "Singularity in Average Information Matrix"? how to do?

From: <arthur.gilmour_at_DPI.NSW.GOV.AU>
Date: Tue, 28 Oct 2008 08:41:22 +1100

Dear Luan Sheng,

Further to my response last night,
What if genetic is just the dam component?
I am not very familiar with fish experiments but I understand that
sometimes families are raised in different tubs. Since in this case,
families are represented by sires, if these families were raised in
different tubs, then the sire variance is tub variance (in the sire dam
model), and the dam variance is primarily genetic. Under this scenario,
sire is analgous to 'maternal environment' effects in animal experiments.
I have therefore fitted sire + dam (allowing for 6 outliers and on the log
scale with the model, see below)
 log(wt) ~ mu age out(53) out(301) out(302) out(342) out(1004) out(631) !r
sire dam

This gives
 Source Model terms Gamma Component Comp/SE %
 dam 13 13 0.747327 0.104939 1.09 0
 sire 26 26 1.40185 0.196846 2.50 0
 Variance 1300 1292 1.00000 0.140419 25.18 0

The dam variance is still too large to provide a plausible heritability
though. That is, the residual still goes to the boundary in the 'sire +
animal' model because 0.104939 > 0.140419/3
The bottom line is that there appears to be family effects over and above
simple genetic effects. Maybe you need to replicate at the family level so
that you can partition the variance better.

May Jesus Christ continue to be gracious to you,

Arthur Gilmour, His servant .
Mixed model regression mapping for QTL detection in experimental crosses.
Computational Statistics and Data Analysis 51:3749-3764 at

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NSW Department of Primary Industries
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Received on Thu Oct 28 2008 - 08:41:22 EST

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