RooArgSet(x,y,wgt),WeightVar(wgt)) ;
</pre> 

<li>
  The <tt>RooHist</tt> class that represents data as a histogram in a <tt>RooPlot</tt> has been modified
  so that it can show approximate Poisson errors for non-integer data. These approximate
  errors are calculated from interpolation of the error bars of the nearest integers. NB: A weighted dataset
  plotted with <tt>RooAbsData::plotOn()</tt> will be default show sum-of-weights-squared errors. Only
  when Poisson error are forced through a <tt>DataError(