code: public static RegressionDataSet loadR(File file, double sparseRatio, int vectorLength) throws FileNotFoundException, IOException
      {
          return loadR(new FileReader(file), sparseRatio, vectorLength);
      }
docs: Loads a new regression data set from a LIBSVM file, assuming the label is
  a numeric target value to predict
  
  @param file the file to load
  @param sparseRatio the fraction of non zero values to qualify a data
  point as sparse
  @param vectorLength the pre-determined length of each vector. If given a
  negative value, the largest non-zero index observed in the data will be
  used as the length.
  @return a regression data set
  @throws FileNotFoundException if the file was not found
  @throws IOException if an error occurred reading the input stream