Contents
What is an rpart model?
Introduction. Rpart is a powerful machine learning library in R that is used for building classification and regression trees. This library implements recursive partitioning and is very easy to use.
What is Xerror in rpart?
The x-error is the cross-validation error (generated by the rpart built-in cross validation). Each level in the Pruning table is the depth of the tree where each of the corresponding values were calculated. This can help you make a decision on where to prune the tree.
How is Xerror calculated rpart?
It should be easy to calculate the rate of the trivial tree, because it assigns all cases to the same class — the class that minimizes the rate. In general, xerror is computed from the misclassification *risk*, which takes into account the loss matrix.
When to use a model in the RPART function?
If the input value for model is a model frame (likely from an earlier call to the rpart function), then this frame is used rather than constructing new data. keep a copy of the x matrix in the result. keep a copy of the dependent variable in the result. If missing and model is supplied this defaults to FALSE.
How is rpart used to split the activity vector?
In the first dataset, we did not specify that Activity was an ordered factor, so rpart tested every possible way to split the levels of the Activity vector. In the second dataset, Activity was specified as an ordered factor so rpart only tested splits that separated the ordered set of Activity levels.
How to change the default in rpart gormanalysis?
To alter the default, equal penalization of mislabeled target classes set the loss component of the parms parameter to a matrix where the (i,j) element is the penalty for misclassifying an i as a j. (The loss matrix must have 0s in the diagonal). For example, consider the following training data.
What is the overall measure of variable importance in rpart?
From the rpart documentation, “An overall measure of variable importance is the sum of the goodness of split measures for each split for which it was the primary variable…” When rpart grows a tree it performs 10-fold cross validation on the data.