title: Random Forest on large xdf files without reading into a dataframe
body: <p>Is there a way to run random forest on large (about 10gb) xdf (revolution R format) files? Obviously I can try rxReadXdf and covert it to a dataframe...but my machine only has 8gb ram and I may be dealing with even larger data sets in the future. For example, using the foreach loop, I will like to run 1000 trees on my quad core machine:</p>
  
  <pre><code>#'train.xdf" is a 10gb training data set
  rf&lt;- foreach(ntree=rep(250, 4), .combine=combine, 
               .packages='randomForest') %do%
      randomForest(amount2~.,data="train", ntree=ntree, importance=TRUE,
                   na.action=na.omit, replace=FALSE)
  </code></pre>
  
  <p>But randomForest is unable to take in "train" (an xdf) file. Is there a way to run random forest directly on xdf without reading into a dataframe? </p>
  
  <p>Cheers,
  agsub </p>