[R] gamm

From: Piet Bell <pj.bell_at_yahoo.co.uk>
Date: Tue 04 Jul 2006 - 04:26:03 EST


Hello,    

  I am a bit confused about gamm in mgcv. Consulting Wood (2006) or Ruppert et al. (2003) hasn't taken away my confusion.    

  In this code from the gamm help file:    

     b2<-gamm(y~s(x0)+s(x1)+s(x2)+s(x3),family=poisson,random=list(fac=~1))

  Am I correct in assuming that we have a random intercept here....but that the amount of smoothing is also changing per level of the factor?? Or is it only the intercept that is changing?        

  And where can I find some explanation on the magic output below?    

  Thanks
  Piet        

  summary(b2$lme)
  Random effects:
 Formula: ~Xr.1 - 1 | g.1
 Structure: pdIdnot

           Xr.11 Xr.12 Xr.13 Xr.14 Xr.15 Xr.16 Xr.17 Xr.18 StdDev: 1.680679 1.680679 1.680679 1.680679 1.680679 1.680679 1.680679 1.680679

   Formula: ~Xr.2 - 1 | g.2 %in% g.1
 Structure: pdIdnot

          Xr.21 Xr.22 Xr.23 Xr.24 Xr.25 Xr.26 Xr.27 Xr.28 StdDev: 1.57598 1.57598 1.57598 1.57598 1.57598 1.57598 1.57598 1.57598

   Formula: ~Xr.3 - 1 | g.3 %in% g.2 %in% g.1  Structure: pdIdnot

           Xr.31 Xr.32 Xr.33 Xr.34 Xr.35 Xr.36 Xr.37 Xr.38 StdDev: 20.06377 20.06377 20.06377 20.06377 20.06377 20.06377 20.06377 20.06377

   Formula: ~Xr.4 - 1 | g.4 %in% g.3 %in% g.2 %in% g.1  Structure: pdIdnot

               Xr.41 Xr.42 Xr.43 Xr.44 Xr.45 StdDev: 0.0001063304 0.0001063304 0.0001063304 0.0001063304 0.0001063304

               Xr.46 Xr.47 Xr.48 StdDev: 0.0001063304 0.0001063304 0.0001063304

   Formula: ~1 | fac %in% g.4 %in% g.3 %in% g.2 %in% g.1

        (Intercept) Residual
StdDev: 0.6621173 1.007227
  Variance function:

 Structure: fixed weights
 Formula: ~invwt
Fixed effects: y.0 ~ X - 1

                  Value Std.Error  DF   t-value p-value
X(Intercept)  2.0870364 0.3337787 392  6.252755  0.0000
Xs(x0)Fx1    -0.0000325 0.1028794 392 -0.000316  0.9997
Xs(x1)Fx1     0.3831694 0.0957323 392  4.002509  0.0001
Xs(x2)Fx1     1.4584330 0.3909237 392  3.730736  0.0002
Xs(x3)Fx1 -0.0123951 0.0143162 392 -0.865809 0.3871  Correlation:                                                      

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