How to select the value of mfinal in boosting



I am currently studying about boosting I came across a attribute mfinal which is number of tree .I want to know how to decided what should be value mfinal so that that predication of classifier will improve.In an example I have taken mfinal =10 just for creating model I want to check is it the best value of mfinal

sub <- c(sample(1:50, 25), sample(51:100, 25), sample(101:150, 25))
iris.adaboost <- boosting(Species ~ ., data=iris[sub,], mfinal=10)
iris.predboosting<- predict.boosting(iris.adaboost, newdata=iris[-sub,])


You should check the margin to decide if 10 is enough . I forgot the parameter in Adabag. Do you need this urgently?