Find out which predictor variables are actually used in the random forest.
An object of class
Should the list of variables used be broken down by trees in the forest?
Should the frequencies that variables appear in trees be returned?
by.tree=FALSE, a integer vector containing
frequencies that variables are used in the forest. If
by.tree=TRUE, a matrix is returned, breaking down the counts by
tree (each column corresponding to one tree and each row to a variable).
by.tree=TRUE, a list of integer
indices is returned giving the variables used in the trees, else if
by.tree=FALSE, a vector of integer indices giving the
variables used in the entire forest.
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