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Caret and GBM Errors

I am trying to use a carriage package in R for several nested cross-validation processes with "user-defined" performance metrics. I had all kinds of problems, so I stepped back to see if there were problems with a lot of box use in the carriage, and it looks like I ran into it.

If I run the following:

install.packages("caret") install.packages("gbm") library(caret) library(gbm) data(GermanCredit) GermanCredit$Class<-ifelse(GermanCredit$Class=='Bad',1,0) gbmGrid <- expand.grid(.interaction.depth = 1, .n.trees = 150, .shrinkage = 0.1) gbmMOD <- train(Class~., data=GermanCredit ,method = "gbm", tuneGrid= gbmGrid, distribution="bernoulli", bag.fraction = 0.5, train.fraction = 0.5, n.minobsinnode = 10, cv.folds = 1, keep.data=TRUE, verbose=TRUE )

I get an error (or similar):

  Error in { : task 1 failed - "arguments imply differing number of rows: 619, 381"

with warnings:

 1: In eval(expr, envir, enclos) : model fit failed for Resample01: interaction.depth=1, n.trees=150, shrinkage=0.1

But, if I run only the gbm procedure, everything ends perfectly.

 gbm1 <- gbm(Class~., data=GermanCredit, distribution="bernoulli", n.trees=150, # number of trees shrinkage=0.10, interaction.depth=1, bag.fraction = 0.5, train.fraction = 0.5, n.minobsinnode = 10, cv.folds = 1, keep.data=TRUE, verbose=TRUE )
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2 answers

There were two problems: passing cv.folds caused the problem. In addition, you do not need to convert the result to a binary number; this makes train think this is a regression problem. The idea behind the train function is to smooth out inconsistencies with modeling functions, so we use factors for classification and numbers for regression.

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Just for a note - although this problem was caused by the reason described in the answer, the error message (below) can also occur with an older version of the carriage and gbm. I encountered this error and, having spent a lot of time figuring out what the problem was, it turned out I had to upgrade to the latest version of cat (5.17-7) and gbm (2.1-0.1). This is the latest version to date on CRAN.

 Error in { : task 1 failed - "arguments imply differing number of rows: ...
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