COBRA : COBRA.lars: no visible global function definition for ‘lars’
COBRA : COBRA.lars: no visible global function definition for
  ‘predict.lars’
COBRA : COBRA.tree: no visible global function definition for ‘tree’
COBRA : COBRA.tree: no visible global function definition for
  ‘as.formula’
COBRA : COBRA.tree: no visible global function definition for ‘predict’
COBRA : COBRA.ridge: no visible global function definition for
  ‘linearRidge’
COBRA : COBRA.ridge: no visible global function definition for
  ‘as.formula’
COBRA : COBRA.ridge: no visible global function definition for
  ‘predict’
COBRA : COBRA.randomForest: no visible global function definition for
  ‘randomForest’
COBRA : COBRA.randomForest: no visible global function definition for
  ‘predict’
COBRA: no visible global function definition for ‘sfInit’
COBRA: no visible global function definition for ‘sfLibrary’
COBRA: no visible global function definition for ‘sfExportAll’
COBRA: no visible global function definition for ‘sfSapply’
COBRA: no visible global function definition for ‘sfStop’
COBRA: no visible global function definition for ‘write.table’
COBRA: no visible global function definition for ‘pdf’
COBRA: no visible global function definition for ‘plot’
COBRA: no visible global function definition for ‘points’
COBRA: no visible global function definition for ‘legend’
COBRA: no visible global function definition for ‘abline’
COBRA: no visible global function definition for ‘lines’
COBRA: no visible global function definition for ‘dev.off’
COBRA: no visible global function definition for ‘dev.new’
Undefined global functions or variables:
  abline as.formula dev.new dev.off lars legend linearRidge lines pdf
  plot points predict predict.lars randomForest sfExportAll sfInit
  sfLibrary sfSapply sfStop tree write.table
Consider adding
  importFrom("grDevices", "dev.new", "dev.off", "pdf")
  importFrom("graphics", "abline", "legend", "lines", "plot", "points")
  importFrom("stats", "as.formula", "predict")
  importFrom("utils", "write.table")
to your NAMESPACE file.