boosting {adabag} | R Documentation |

Fits the AdaBoost.M1 (Freund and Schapire, 1996) and SAMME (Zhu et al., 2009) algorithms using classification trees as single classifiers.

```
boosting(formula, data, boos = TRUE, mfinal = 100, coeflearn = 'Breiman',
control,...)
```

`formula` |
a formula, as in the |

`data` |
a data frame in which to interpret the variables named in |

`boos` |
if |

`mfinal` |
an integer, the number of iterations for which boosting is run
or the number of trees to use. Defaults to |

`coeflearn` |
if 'Breiman'(by default), |

`control` |
options that control details of the rpart algorithm. See rpart.control for more details. |

`...` |
further arguments passed to or from other methods. |

AdaBoost.M1 and SAMME are simple generalizations of AdaBoost for more than two classes. In AdaBoost-SAMME the individual trees are required to have an error lower than 1-1/nclasses instead of 1/2 of the AdaBoost.M1

An object of class `boosting`

, which is a list with the following components:

`formula` |
the formula used. |

`trees` |
the trees grown along the iterations. |

`weights` |
a vector with the weighting of the trees of all iterations. |

`votes` |
a matrix describing, for each observation, the number of trees that assigned it to each class, weighting each tree by its |

`prob` |
a matrix describing, for each observation, the posterior probability or degree of support of each class. These probabilities are calculated using the proportion of votes in the final ensemble. |

`class` |
the class predicted by the ensemble classifier. |

`importance` |
returns the relative importance of each variable in the classification task. This measure takes into account the gain of the Gini index given by a variable in a tree and the weight of this tree. |

Esteban Alfaro-Cortes Esteban.Alfaro@uclm.es, Matias Gamez-Martinez Matias.Gamez@uclm.es and Noelia Garcia-Rubio Noelia.Garcia@uclm.es

Alfaro, E., Gamez, M. and Garcia, N. (2013): “adabag: An R Package for Classification with Boosting and Bagging”. Journal of Statistical Software, Vol 54, 2, pp. 1–35.

Alfaro, E., Garcia, N., Gamez, M. and Elizondo, D. (2008): “Bankruptcy forecasting: An empirical comparison of AdaBoost and neural networks”. Decision Support Systems, 45, pp. 110–122.

Breiman, L. (1998): “Arcing classifiers”. The Annals of Statistics, Vol 26, 3, pp. 801–849.

Freund, Y. and Schapire, R.E. (1996): “Experiments with a new boosting algorithm”. In Proceedings of the Thirteenth International Conference on Machine Learning, pp. 148–156, Morgan Kaufmann.

Zhu, J., Zou, H., Rosset, S. and Hastie, T. (2009): “Multi-class AdaBoost”. Statistics and Its Interface, 2, pp. 349–360.

```
## rpart library should be loaded
data(iris)
iris.adaboost <- boosting(Species~., data=iris, boos=TRUE, mfinal=3)
iris.adaboost
## Data Vehicle (four classes)
library(mlbench)
data(Vehicle)
l <- length(Vehicle[,1])
sub <- sample(1:l,2*l/3)
mfinal <- 3
maxdepth <- 5
Vehicle.rpart <- rpart(Class~.,data=Vehicle[sub,],maxdepth=maxdepth)
Vehicle.rpart.pred <- predict(Vehicle.rpart,newdata=Vehicle[-sub, ],type="class")
tb <- table(Vehicle.rpart.pred,Vehicle$Class[-sub])
error.rpart <- 1-(sum(diag(tb))/sum(tb))
tb
error.rpart
Vehicle.adaboost <- boosting(Class ~.,data=Vehicle[sub, ],mfinal=mfinal, coeflearn="Zhu",
control=rpart.control(maxdepth=maxdepth))
Vehicle.adaboost.pred <- predict.boosting(Vehicle.adaboost,newdata=Vehicle[-sub, ])
Vehicle.adaboost.pred$confusion
Vehicle.adaboost.pred$error
#comparing error evolution in training and test set
errorevol(Vehicle.adaboost,newdata=Vehicle[sub, ])->evol.train
errorevol(Vehicle.adaboost,newdata=Vehicle[-sub, ])->evol.test
plot.errorevol(evol.test,evol.train)
```

[Package *adabag* version 5.0 Index]