title: Extract raw data from affyBatch object
body: <p>I have an affyBatch object with gene expression data.  The data is read in using
      dat &lt;- ReadAffy()
  with no options.  I then extract the 5600 genes that I am interested in using,
      dat &lt;- RemoveProbes(listOutProbeSets, cdfpackagename, probepackagename)</p>
  
  <p>I then normalise the expression data using
      dat.rma &lt;- rma(dat)</p>
  
  <p>Now I want to the export the raw data AND the rma-normalised data to .csv files.  Inspecting the data I find that exprs(dat) has dimensions 226576 by 30 and dat.rma has dimensions 5600 by 30.  How do I extract the 5600 by 30 matrix of the RAW expression values?  I don't know where the 226576 rows in the raw data have come from!</p>
  
  <p>I'm a bit of a beginner with bioconductor data structures!  Sorry for not providing runnable example code - not sure how I would do that in this case.</p>