def addRasterPoints(self, xdata, repnum, plotname=None):
        """Add a list (or numpy array) of points to raster plot, 
        in any order.

        :param xdata: bin centers
        :param ydata: rep number 
        """
        if plotname is None:
            plotname = self.responsePlots.keys()[0]
        ydata = np.ones_like(xdata)*repnum
        self.responsePlots[plotname].appendData('raster', xdata, ydata)