fbed.glmm.reg: Forward Backward Early Dropping selection regression with...

In MXM: Feature Selection (Including Multiple Solutions) and Bayesian Networks

Forward Backward Early Dropping selection regression with GLMM

Description

Forward Backward Early Dropping selection regression with GLMM.

Usage

fbed.glmm.reg(target, dataset, id, prior = NULL, reps = NULL, ini = NULL, 
threshold = 0.05, wei = NULL, K = 0, method = "LR", gam = NULL, 
backward = TRUE, test = "testIndGLMMReg")

Arguments

target	The class variable. This can be a numerical vector with continuous data, binary or discrete valued data. It can also be a factor variable with two levels only.
dataset	The dataset; provide a numerical a matrix (columns = variables, rows = observations).
id	This is a numerical vector of the same size as target denoting the groups or the subjects.
prior	If you have prior knowledge of some variables that must be in the variable selection phase add them here. This an be a vector (if you have one variable) or a matrix (if you more variables). This does not work during the backward phase at the moment.
reps	This is a numerical vector of the same size as target denoting the groups or the subjects. If you have longitudinal data and you know the time points, then supply them here.
ini	If you already have the test statistics and the p-values of the univariate associations (the first step of FBED) supply them as a list with the names "stat" and "pvalue" respectively in the case of method = "LR". In the case of method = "eBIC" this is a list with an element called "bic".
threshold	Threshold (suitable values in (0, 1)) for asmmmbsing p-values significance. Default value is 0.05.
wei	A vector of weights to be used for weighted regression. The default value is NULL.
K	How many times should the process be repated? The default value is 0.
method	Do you want the likelihood ratio test to be performed ("LR" is the default value) or perform the selection using the "eBIC" criterion (BIC is a special case).
gam	In case the method is chosen to be "eBIC" one can also specify the gamma parameter. The default value is "NULL", so that the value is automatically calculated.
backward	After the Forward Early Dropping phase, the algorithm proceeds witha the usual Backward Selection phase. The default value is set to TRUE. It is advised to perform this step as maybe some variables are false positives, they were wrongly selected. The backward phase using likelihood ratio test and eBIc are two different functions and can be called directly by the user. SO, if you want for example to perform a backard regression with a different threshold value, just use these two functions separately.
test	This is for the type of regression to be used, "testIndGLMMReg", for Gaussian regression, "testIndGLMMLogistic for logistic regression or "testIndGLMMPois" for Poisson regression, "testIndGLMMGamma" for Gamma regression and "testIndGLMMNormLog" for Gaussian regression with log link and "testIndGLMMOrdinal" for ordinal regression.

Details

The algorithm is a variation of the usual forward selection. At every step, the most significant variable enters the selected variables set. In addition, only the significant variables stay and are further examined. The non signifcant ones are dropped. This goes until no variable can enter the set. The user has the option to redo this step 1 or more times (the argument K). In the end, a backward selection is performed to remove falsely selected variables.

Bear in mind that for the "gaussian" case, the forward phase takes place using the F test (Wald statistic calibrated against an F distribution). The backward phase though takes place using the log-likelihood ratio test.

If you specify a range of values of K it returns the results of fbed.reg for this range of values of K. For example, instead of runnning fbed.reg with K=0, K=1, K=2 and so on, you can run fbed.reg with K=0:2 and the selected variables found at K=2, K=1 and K=0 are returned. Note also, that you may specify maximum value of K to be 10, but the maximum value FBED used was 4 (for example).

Value

If K is a single number a list including:

res	A matrix with the selected variables, their test statistic and the associated logged p-value.
info	A matrix with the number of variables and the number of tests performed (or models fitted) at each round (value of K). This refers to the forward phase only.
runtime	The runtime required.
back.rem	The variables removed in the backward phase.
back.n.tests	The number of models fitted in the backward phase.

If K is a sequence of numbers a list tincluding:

univ	If you have used the log-likelihood ratio test this list contains the test statistics and the associated p-values of the univariate associations tests. If you have used the EBIc this list contains the eBIC of the univariate associations.
res	The results of fbed.glmm.reg with the maximum value of K.
mod	A list where each element refers to a K value. If you run FBED with method = "LR" the selected variables, their test statistic and their p-value is returned. If you run it with method = "eBIC", the selected variables and the eBIC of the model with those variables are returned.

Author(s)

Michail Tsagris

R implementation and documentation: Michail Tsagris [e-mail]

References

Borboudakis G. and Tsamardinos I. (2019). Forward-backward selection with early dropping. Journal of Machine Learning Research, 20(8): 1-39.

Eugene Demidenko (2013). Mixed Models: Theory and Applications with R, 2nd Edition. New Jersey: Wiley & Sons.

See Also

fbed.gee.reg, glmm.bsreg, MMPC.glmm, cv.fbed.lmm.reg

Examples

## Not run: 
require(lme4)
data(sleepstudy)
reaction <- sleepstudy$Reaction
subject <- sleepstudy$Subject
x <- matrix(rnorm(180 * 200),ncol = 200) ## unrelated predictor variables
m1 <- fbed.glmm.reg(reaction, cbind(x1, x), subject) 
m2 <- MMPC.glmm(target = reaction, group = subject, dataset = x)

## End(Not run)

MXM documentation built on Aug. 25, 2022, 9:05 a.m.