[R] predict.gl( ..., type="terms" )

BXC (Bendix Carstensen) bxc at steno.dk
Tue Apr 6 23:11:52 CEST 2004


When I do:

> apc <- glm( D ~ ns( Ax, knots=seq(50,80,10), Bo=c(40,90) ) +
+                 ns( Cx, knots=seq(1880,1940,20), Bo=c(1840,1960) ) +
+                 ns( Px, knots=seq(1960,1980,10), Bo=c(1940,2000) ) +
+                 offset( log( Y ) ),
+             family=poisson )
> pterm <-  predict( apc, type="terms" )
> plink <-  predict( apc, type="link" )
> ( apply( pterm, 1, sum ) + log( Y ) - plink )[1:10]
      1       2       3       4       5       6       7       8       9
10 
6.85047 6.85047 6.85047 6.85047 6.85047 6.85047 6.85047 6.85047 6.85047
6.85047 
> coef( apc )[1] 
(Intercept) 
  -13.61998 

>From the help page for predict.glm I would have expected that the
constant 6.85 
was -intercept.

What am I missing from predict.glm? (or from splines?)

Bendix Carstensen

----------------------
Bendix Carstensen
Senior Statistician
Steno Diabetes Center
Niels Steensens Vej 2
DK-2820 Gentofte
Denmark
tel: +45 44 43 87 38
mob: +45 30 75 87 38
fax: +45 44 43 07 06
bxc at steno.dk
www.biostat.ku.dk/~bxc




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