Workaround "n.trees" is missing in R package gbm version 2.1.1

Just short note to anyone encountering following error in the gbm package version 2.1.1:

 Error in paste("Using", n.trees, "trees...\n") : 
  argument "n.trees" is missing, with no default 

This issue will be fixed in the next version but in the mean time I'll post my workaround. If you add following function to your code then everything should work:

## work around bug in gbm 2.1.1
predict.gbm <- function (object, newdata, n.trees, type = "link", single.tree = FALSE, ...) {
  if (missing(n.trees)) {
    if (object$train.fraction < 1) {
      n.trees <- gbm.perf(object, method = "test", plot.it = FALSE)
    }
    else if (!is.null(object$cv.error)) {
      n.trees <- gbm.perf(object, method = "cv", plot.it = FALSE)
    }
    else {
      n.trees <- length(object$train.error)
    }
    cat(paste("Using", n.trees, "trees...\n"))
    gbm::predict.gbm(object, newdata, n.trees, type, single.tree, ...)
  }
}