Description Usage Arguments Details Value Author(s) References See Also Examples
This routine helps in finding an optimum step-size modification factor for GAMBoost
, i.e., that results in an optimum in terms of cross-validated log-likelihood.
1 2 3 4 |
x |
|
y |
response vector of length |
x.linear |
optional |
direction |
direction of line search for an optimal step-size modification factor (starting from value 1). |
start.stepsize |
step size used for the line search. A final step is performed using half this size. |
iter.max |
maximum number of search iterations. |
constant.cv.res |
result of |
parallel |
logical value indicating whether evaluation of cross-validation folds should be performed in parallel
on a compute cluster. This requires library |
trace |
logical value indicating whether information on progress should be printed. |
... |
miscellaneous parameters for |
A coarse line search is performed for finding the best parameter stepsize.factor.linear
for GAMBoost
. If an pendistmat.linear
argument is provided (which is passed on to GAMBoost
), a search for factors smaller than 1 is sensible (corresponding to direction="down"
). If no connection information is provided, it is reasonable to employ direction="both"
, for avoiding restrictions without subject matter knowledge.
List with the following components:
factor.list |
array with the evaluated step-size modification factors. |
critmat |
matrix with the mean log-likelihood for each step-size modification factor in the course of the boosting steps. |
optimal.factor.index |
index of the optimal step-size modification factor. |
optimal.factor |
optimal step-size modification factor. |
optimal.step |
optimal boosting step number, i.e., with minimum mean log-likelihood, for step-size modification factor |
Written by Harald Binder binderh@uni-mainz.de.
Binder, H. and Schumacher, M. (2009). Incorporating pathway information into boosting estimation of high-dimensional risk prediction models. BMC Bioinformatics. 10:18.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | ## Not run:
## Generate some data
n <- 100; p <- 10
# covariates with non-linear (smooth) effects
x <- matrix(runif(n*p,min=-1,max=1),n,p)
eta <- -0.5 + 2*x[,1] + 2*x[,3]^2 + x[,9]-.5
y <- rbinom(n,1,binomial()$linkinv(eta))
# Determine step-size modification factor for a generalize linear model
# As there is no connection matrix, perform search into both directions
optim.res <- optimStepSizeFactor(direction="both",
y=y,x.linear=x,family=binomial(),
penalty.linear=200,
trace=TRUE)
# Fit with obtained step-size modification parameter and optimal number of boosting
# steps obtained by cross-validation
gb1 <- GAMBoost(x=NULL,y=y,x.linear=x,family=binomial(),penalty.linear=200,
stepno=optim.res$optimal.step,
stepsize.factor.linear=optim.res$optimal.factor)
summary(gb1)
## End(Not run)
|
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