feature_selection: Feature selection

In mlampros/FeatureSelection: Feature extraction and selection based on 'glmnet', 'xgboost' and 'ranger'

Feature selection

Description

This function uses three different methods (glmnet, xgboost, ranger) in order to select important features.

Usage

feature_selection(
  X,
  y,
  method = NULL,
  params_glmnet = NULL,
  params_xgboost = NULL,
  params_ranger = NULL,
  xgb_sort = NULL,
  CV_folds = 5,
  stratified_regr = FALSE,
  scale_coefs_glmnet = FALSE,
  cores_glmnet = NULL,
  verbose = FALSE
)

Arguments

X	a sparse Matrix, a matrix or a data frame
y	a vector of length representing the response variable
method	one of 'glmnet-lasso', 'xgboost', 'ranger'
params_glmnet	a list of parameters for the glmnet model
params_xgboost	a list of parameters for the xgboost model
params_ranger	a list of parameters for the ranger model
xgb_sort	sort the xgboost features by "Gain", "Cover" or "Frequency" ( defaults to "Frequency")
CV_folds	a number specifying the number of folds for cross validation
stratified_regr	a boolean determining if the folds in regression should be stratified
scale_coefs_glmnet	if TRUE, less important coefficients will be smaller than the more important ones (ranking/plotting by magnitude possible)
cores_glmnet	an integer determining the number of cores to register in glmnet
verbose	outputs info

Details

This function returns the important features using one of the glmnet, xgboost or ranger algorithms. The glmnet algorithm can take either a sparse matrix, a matrix or a data frame and returns a data frame with non zero coefficients. The xgboost algorithm can take either a sparse matrix, a matrix or a data frame and returns the importance of the features in form of a data frame, furthermore it is possible to sort the features using one of the "Gain", "Cover" or "Frequency" methods. The ranger algorithm can take either a matrix or a data frame and returns the important features using one of the 'impurity' or 'permutation' methods.

Value

a data frame with the most important features

Author(s)

Lampros Mouselimis

Examples

## Not run: 

#...........
# regression
#...........

data(iris)

X = iris[, -5]
y = X[, 1]
X = X[, -1]

params_glmnet = list(alpha = 1,
                     family = 'gaussian',
                     nfolds = 3,
                     parallel = TRUE)

res = feature_selection(X,
                        y,
                        method = 'glmnet-lasso',
                        params_glmnet = params_glmnet,
                        CV_folds = 5,
                        cores_glmnet = 5)

#......................
# binary classification
#......................

y = iris[, 5]
y = as.character(y)
y[y == 'setosa'] = 'virginica'
X = iris[, -5]

params_ranger = list(write.forest = TRUE,
                     probability = TRUE,
                     num.threads = 6,
                     num.trees = 50,
                     verbose = FALSE,
                     classification = TRUE,
                     mtry = 2,
                     min.node.size = 5,
                     importance = 'impurity')

res = feature_selection(X,
                        y,
                        method = 'ranger',
                        params_ranger = params_ranger,
                         CV_folds = 5)

#..........................
# multiclass classification
#..........................

y = iris[, 5]
multiclass_xgboost = ifelse(y == 'setosa', 0, ifelse(y == 'virginica', 1, 2))
X = iris[, -5]

params_xgboost = list(params = list("objective" = "multi:softprob",
                                    "bst:eta" = 0.35,
                                    "subsample" = 0.65,
                                     "num_class" = 3,
                                     "max_depth" = 6,
                                     "colsample_bytree" = 0.65,
                                     "nthread" = 2),
                        nrounds = 50,
                         print.every.n = 50,
                         verbose = 0,
                         maximize = FALSE)

res = feature_selection(X,
                        multiclass_xgboost,
                        method = 'xgboost',
                        params_xgboost = params_xgboost,
                        CV_folds = 5)

## End(Not run)

mlampros/FeatureSelection documentation built on Aug. 12, 2024, 12:30 p.m.