Functions of variance components and their standard errors can be obtained from the vpredict() function. As the variance parameter names can sometimes be long, the variance parameters are represented in vpredict() by the strings “V1”, “V2”,… in the order they appear in the vparameters component of the asreml object.
By default, for simple models ASReml fits on the ‘gamma’ scale, which means that the returned variance components are variance ratios (for more details please see the ASReml-R Reference Manual, version 4). Therefore, you have to be careful as ASReml-R does not automatically convert variance ratios to variance components or their standard errors. You can fit the model on the component scale if you want to use vpredict() and the standard errors.
Method
ADD : residual = ~idv(units). This will add an additional variance component to the model, that will be fixed to one. For example:
head(harvey)
head(harvey.ped)
harvey.ainv <- ainverse(harvey.ped)
adg0.asr <- asreml(y3 ~ Line,
random = ~vm(Calf, harvey.aiv),
residual = ~idv(units),
data = harvey)
> summary(adg0.asr)$varcomp
component std.error z.ratio bound %ch
vm(Calf, harvey.ainv) 499.5204 500.5139 0.9980149 P 0
units!units 273.1669 410.0206 0.6662273 P 0
units!R 1.0000 NA NA F 0
> # Heritability
> vpredict(adg0.asr, hA ~ V1/(V1 + V2))
Estimate
SEhA 0.6464716 0.5658723