Calculates the margins
Calculates the margins of an AdaBoost.M1, AdaBoost-SAMME or Bagging classifier for a data frame
margins(object, newdata)
object |
This object must be the output of one of the functions |
newdata |
The same data frame used for building the |
Intuitively, the margin for an observation is related to the certainty of its classification. It is calculated as the difference between the support of the correct class and the maximum support of an incorrect class
An object of class margins, which is a list with only one component:
margins |
a vector with the margins. |
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.
Schapire, R.E., Freund, Y., Bartlett, P. and Lee, W.S. (1998): “Boosting the margin: A new explanation for the effectiveness of voting methods”. The Annals of Statistics, vol 26, 5, pp. 1651–1686.
#Iris example library(rpart) data(iris) sub <- c(sample(1:50, 25), sample(51:100, 25), sample(101:150, 25)) iris.adaboost <- boosting(Species ~ ., data=iris[sub,], mfinal=3) margins(iris.adaboost,iris[sub,])->iris.margins # training set plot.margins(iris.margins) # test set iris.predboosting<- predict.boosting(iris.adaboost, newdata=iris[-sub,]) margins(iris.predboosting,iris[-sub,])->iris.predmargins plot.margins(iris.predmargins,iris.margins) #Examples with bagging iris.bagging <- bagging(Species ~ ., data=iris[sub,], mfinal=3) margins(iris.bagging,iris[sub,])->iris.bagging.margins # training set iris.predbagging<- predict.bagging(iris.bagging, newdata=iris[-sub,]) margins(iris.predbagging,iris[-sub,])->iris.bagging.predmargins # test set par(bg="lightyellow") plot.margins(iris.bagging.predmargins,iris.bagging.margins)
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