def rmswidth(self, floor=0):
        """Calculate :ref:`pysynphot-formula-rmswidth`.

        Parameters
        ----------
        floor : float
            Throughput values equal or below this threshold are not
            included in the calculation. By default (0), all points
            are included.

        Returns
        -------
        ans : float
            RMS band width.

        """
        mywaveunits = self.waveunits.name
        self.convert('angstroms')

        wave = self.wave
        thru = self.throughput
        self.convert(mywaveunits)

        if floor != 0:
            idx = N.where(thru >= floor)
            wave = wave[idx]
            thru = thru[idx]

        integrand = (wave-self.avgwave())**2 * thru
        num = self.trapezoidIntegration(wave, integrand)
        den = self.trapezoidIntegration(wave, thru)

        if 0.0 in (num, den):
            return 0.0
        else:
            ans = math.sqrt(num/den)
            return ans
Calculate :ref:`pysynphot-formula-rmswidth`.

        Parameters
        ----------
        floor : float
            Throughput values equal or below this threshold are not
            included in the calculation. By default (0), all points
            are included.

        Returns
        -------
        ans : float
            RMS band width.