Re: Interpretation of Components for Splines
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Re: Interpretation of Components for Splines

See the paper by White et al. in Journal of Dairy Science (1999) 82:632-638.

> >The component for spl(time) is a variance component, but it controls the
> >amount of smoothing. If this component (actually the ratio gamma) tends 
> >to zero, the spline fit tends to a straight line, as it gets large the 
> >fit tends to interpolation. The additional variance component, ie 
> >dev(time), allows for the presence of group effects, and can only be 
> >fitted if there is replication at each (or most) time point. This is in 
> >line with the usual one-way random effects analysis where you would fit 
> >y~ mu !r group
> >in asreml to get correct analysis ie estimating both an error and between 
> >groups variance.
> >
> >The usual roughness penalty that is described in most smoothing texts is 
> >actually lambda = 1/gamma(spl).
> Thank you for your remarks. As you know, it is customary to specify
> heritability as a function of the genetic and total variability. In
> formulating linear functions of the variance components, should the
> components for spl(time) and dev(time) be considered a part of the total
> variability or should one include them in the genetic variation?
> Peter /
> >...........................................................................
> ....
> >      Brian Cullis                       Tel: 02 6938 1855
> >      NSW Agriculture                    Fax: 02 6938 1809
> >      Wagga Agricultural Institute     email:
> >      Pine Gully Rd
> >      WAGGA WAGGA  NSW 2650
> --
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