R help - Oct 2008 - gamboost partial fit prediction

Dear useRs,

I am struggling to use gamboost function form the 'mboost' package. More
precisely, I am trying to extract the *partial fit* for each of the
covariates estimated in a model and I usually end up with this annoying:
"Error
in newdata[[xname]] : subscript out of bounds ". I hope that the lack of
details in my query can be straightforwardly compensated by examining the
following code (I am aware of the additive structure of the estimation,
therefore the excerpt below is supposed to be only a part of my final
solution). If the problem does not become more obvious I will provide more
details.

Thanks in advance,
AS

#### R code ####
rm(list=ls(all=T))
library(mboost)
data(bodyfat)

## Model fit
bf_gam <- gamboost(DEXfat ~ ., data = bodyfat)
aic <- AIC(bf_gam)
fit <- bf_gam[mstop(aic)]

## partial prediction
input <- fit$data$input
i <- sort(unique(fit$ensemble[,1]))[1]
a <- fit$ensembles[fit$ensemble[,1]==i]

### Why this does not work?
a[[1]][[1]]$predict(newdata=90)

	[[alternative HTML version deleted]]