o
 sample features used for training each node for additional speedups.
 Further gains using the ideas from the ICML paper are possible. If you
 use this code please consider citing our ICML paper.

 During training each feature is quantized to lie between [0,nBins-1],
 where nBins&lt;=256. Quantization is expensive and should be performed just
 once if training multiple trees. Note that the second output of the
 algorithm is the quantized data, this can be reused in future training.

 USAGE
  [tree,data,er