TODO (not promised):

* Implement the new scheme of handling classwt in classification.

* Allow categorical predictors with more than 32 categories.

* Use more compact storage of proximity matrix.

* Allow case weights by using the weights in sampling?

========================================================================

Changes in 4.5-2:

* New argument `cutoff' added to predict.randomForest().  The usage is 
  analogous to the same argument to randomForest().

* Added `palette' and `pch' arguments to MDSplot() to allow more user control.

* In randomForest(), allow the forest to be returned in `unsupervised' mode.

* Fixed some inaccuracies in help pages.

* Fixed the way version number of the package is found at start-up.

Changes in 4.5-1:

* In classification, split on a categorical predictor with more than 10
  categories is made more efficient:  For two-class problems, the 
  heuristic presented in Section 4.2.2 of the CART book is used.  
  Otherwise 512 randomly sampled (not necessarily unique) splits are 
  tested, instead of all possible splits.

* New function classCenter() has been added.  It takes a proximity matrix and
  a vector of class labels and compute one prototype per class.

* Added the `Automobile' data from UCI Machine Learning Repository.

* Fixed partialPlot() for categorical predictors (wrong barplot was produced).

* Some re-organization and clean-up of internal C/Fortran code is on-going.

Changes in 4.4-3:

* Added the nPerm argument to randomForest(), which controls the number
  of times the out-of-bag part of each variable is permuted, per tree,
  for computing variable importance.  (Currently only implemented for
  regression.)

* When computing the out-of-bag MSE for each tree for assessing variable
  importance in regression, the total number of cases was wrongly used as 
  the divisor.

* Fixed the default and formula methods of randomForest(), so that the
  `call' component of the returned object calls the generic.

* The `% increase in MSE' measure of variable importance in regression was
  not being computed correctly (should divide sum of squares by number of
  out-of-bag samples rather than total number of samples, for each tree).

* Fixed a bug in na.roughfix.default() that gave warning with matrix input.

Changes in 4.4-2:

* Fixed two memory leaks in the regression code (introduced in 4.3-1).

* Fixed a bug that sometimes caused crash in regression when nodesize
  is set to something larger than default (5).

* Changed the tree structure in regression slightly: "treemap" is replaced
  by "leftDaughter" and "rightDaughter".

Changes in 4.4-1:

* Made slight change in regression code so that it won't split `pure' 
  nodes.  Also fixed the `increase in node purity' importance measure 
  in regression.

* The outscale option in randomForest() is removed.  Use the outlier() 
  function instead.  The default outlier() method can be used with other
  proximity/dissimilarity measures.

* More Fortran subroutines migrated to C.

Changes in 4.3-3:

* Fixed randomForest.formula() so that update() will work.

* Fixed up problem in importance(), which was broken in a couple of ways.

Changes in 4.3-2:

* Fixed a bug that caused crashes in classification if test set data
  are supplied.

Changes in 4.3-1:

* Fixed bugs in sampling cases and variables without replacement.

* Added the rfNews() function to display the NEWS file.  Advertised in
  the start up banner.

* (Not user-visible.)  Translated regression tree building code from 
  Fortran to C.  One perhaps noticeable change is less memory usage.

Changes in 4.3-0:

* Thanks to Adele Cutler, there's now casewise variable importance 
  measures in classification.  Similar feature is also added for 
  regression.  Use the new localImp option in randomForest().

* The `importance' component of randomForest object has been changed:  
  The permutation-based measures are not divided by their `standard 
  errors'.  Instead, the `standard errors' are stored in the 
  `importanceSD' component.  One should use the importance() extractor 
  function rather than something like rf.obj$importance for extracting 
  the importance measures.

* The importance() extractor function has been updated:  If the 
  permutation-based measures are available, calling importance() 
  with only a randomForest object returns the matrix of variable 
  importance measures.  There is the `scale' argument, which defaults 
  to TRUE.

* In predict.randomForest, there is a new argument `nodes' (default to 
  FALSE).  For classification, if nodes=TRUE, the returned object has an
  attribute `nodes', which is an n by ntree matrix of terminal node
  indicators.  This is ignored for regression.

Changes in 4.2-1:

* There is now a package name space.  Only generics are exported.

* Some function names have been changed: 
    partial.plot -> partialPlot
    var.imp.plot -> varImpPlot
    var.used     -> varUsed

* There is a new option `replace' in randomForest() (default to TRUE)
  indicating whether the sampling of cases is with or without
  replacement. 

* In randomForest(), the `sampsize' option now works for both
  classification and regression, and indicate the number of cases to be 
  drawn to grow each tree.  For classification, if sampsize is a vector of
  length the number of classes, then sampling is stratified by class.

* With the formula interface for randomForest(), the default na.action,	
  na.fail, is effective.  I.e., an error is given if there are NAs present
  in the data.  If na.omit is desired, it must be given explicitly.

* For classification, the err.rate component of the randomForest object
  (and the corresponding one for test set) now is a ntree by (nclass + 1)
  matrix, the first column of which contains the overall error rate, and
  the remaining columns the class error rates.  The running output now
  also prints class error rates.  The plot method for randomForest will
  plot the class error rates as well.

* The predict() method now checks whether the variable names in newdata 
  match those from the training data (if the randomForest object is not
  created from the formula interface).

* partialPlot() and varImpPlot() now have optional arguments xlab, ylab
  and main for more flexible labelling.  Also, if a factor is given as
  the variable, a real bar plot is produced.

* partialPlot() will now remove rows with NAs from the data frame given.

* For regression, if proximity=FALSE, an n by n array of integers is 
  erroneously allocated but not used (it's only used for proximity 
  calculation, so not needed otherwise).

* Updated combine() to conform to the new randomForest object.

* na.roughfix() was not working correctly for matrices, which in turns 
  causes problem in rfImpute().

 
Changes in 4.1-0:

* In randomForest(), if sampsize is given, the sampling is now done
  without replacement, in addition to stratified by class.  Therefore 
  sampsize can not be larger than the class frequencies.

* In classification randomForest, checks are added to avoid trees with 
  only the root node.

* Fixed a bug in the Fortran code for classification that caused segfault 
  on some system when encountering a tree with only root node.

* The help page for predict.randomForest() now states the fact that when 
  newdata is not specified, the OOB predictions from the randomForest 
  object is returned.

* plot.randomForest() and print.randomForest() were not checking for 
  existence of performance (err.rate or mse) on test data correctly.
