trainControl(
             method = "boot", 
             number = ifelse(method == "cv", 10, 25), 
             verboseIter = TRUE, 
             returnData = TRUE, 
             returnResamp = "final",
             p = 0.75, 
             summaryFunction = defaultSummary,
             selectionFunction = "best",
             index = NULL)boot, cv,
    LOOCV,  LGOCV (for repeated training/test splits), or
    oob (only for random forest, bagged trees, bagged earth, bagged flexible discriminant analysis,defaultSummary.best for details and other options.