Usage of caret with gbm method for multiclass classification

I am solving a multiclass classification problem and trying to use Generalized Boosted Models (gbm package in R). The issue I faced: caret's `train` function with `method="gbm"` seems not to work with multiclass data properly. A simple example is presented below. ``` library(gbm) library(caret) data(iris) fitControl <- trainControl(method="repeatedcv", number=5, repeats=1, verboseIter=TRUE) set.seed(825) gbmFit <- train(Species ~ ., data=iris, method="gbm", trControl=fitControl, verbose=FALSE) gbmFit ``` The output is ``` + Fold1.Rep1: interaction.depth=1, shrinkage=0.1, n.trees=150 predictions failed for Fold1.Rep1: interaction.depth=1, shrinkage=0.1, n.trees=150 - Fold1.Rep1: interaction.depth=1, shrinkage=0.1, n.trees=150 + Fold1.Rep1: interaction.depth=2, shrinkage=0.1, n.trees=150 ... + Fold5.Rep1: interaction.depth=3, shrinkage=0.1, n.trees=150 predictions failed for Fold5.Rep1: interaction.depth=3, shrinkage=0.1, n.trees=150 - Fold5.Rep1: interaction.depth=3, shrinkage=0.1, n.trees=150 Aggregating results Selecting tuning parameters Fitting interaction.depth = numeric(0), n.trees = numeric(0), shrinkage = numeric(0) on full training set Error in if (interaction.depth < 1) { : argument is of length zero ``` Yet if I try to use gbm without caret wrapper, I get nice results. ``` set.seed(1365) train <- createDataPartition(iris$Species, p=0.7, list=F) train.iris <- iris[train,] valid.iris <- iris[-train,] gbm.fit.iris <- gbm(Species ~ ., data=train.iris, n.trees=200, verbose=FALSE) gbm.pred <- predict(gbm.fit.iris, valid.iris, n.trees=200, type="response") gbm.pred <- as.factor(colnames(gbm.pred)[max.col(gbm.pred)]) ##! confusionMatrix(gbm.pred, valid.iris$Species)$overall ``` FYI, code on line marked by `##!` converts a matrix of class probabilities returned by `predict.gbm` to a factor of most probable classes. The output is ``` Accuracy Kappa AccuracyLower AccuracyUpper AccuracyNull AccuracyPValue McnemarPValue 9.111111e-01 8.666667e-01 7.877883e-01 9.752470e-01 3.333333e-01 8.467252e-16 NaN ``` Any suggestions how to make caret work properly with gbm on multiclass data? UPD: ``` sessionInfo() R version 2.15.3 (2013-03-01) Platform: x86_64-pc-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 LC_PAPER=C LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C attached base packages: [1] splines stats graphics grDevices utils datasets methods base other attached packages: [1] e1071_1.6-1 class_7.3-5 gbm_2.0-8 survival_2.36-14 caret_5.15-61 reshape2_1.2.2 plyr_1.8 [8] lattice_0.20-13 foreach_1.4.0 cluster_1.14.3 compare_0.2-3 loaded via a namespace (and not attached): [1] codetools_0.2-8 compiler_2.15.3 grid_2.15.3 iterators_1.0.6 stringr_0.6.2 tools_2.15.3 ```