[R] degenerate cases in RPART

[john_heumann@agilent.com]

RPART doesn't seem to handle the degenerate case when all training 
samples are drawn from a single class:

  > TrainType
  [1] 0 0 0 0
  > TrainDat
           V1        V2        V3        V4        V5
  1 0.6434392 0.5105860 0.3048803 0.3161728 0.5449632
  2 0.1710005 0.5973921 0.1267061 0.6146834 0.7299928
  3 0.6919125 0.8880789 0.9123243 0.9061885 0.9553663
  4 0.3094843 0.6475508 0.7403838 0.6824748 0.8488170
  > x <- rpart(as.factor(TrainType)~., data=TrainDat)
  > x
  Error in paste(temp, yprob[, i], sep = " ") : 
          subscript out of bounds
  > predict(x, TrainDat)
  Error in predict.rpart(x, TrainDat) : dimnames applied to non-array
  >

Conversely TREE had no problem with this test case, even if the features
are also degenerate (same features for each sample).

Is this expected behavior from RPART or a bug? This is with R1.6.1 on NT4.

Thanks,
-jh-

=================================
John Heumann, Agilent Technologies, Inc.
815 14th. St. S.W., Loveland, CO 80537 
Email: john_heumann at agilent.com
Phone: (970) 679-3761, Fax: (970) 679-5399
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