def sigangledAngle(self,dangle,assumeZeroMean=True,smallest=False,
                       simple=False):
        """
        NAME:

           sigangledAngle

        PURPOSE:

           calculate the dispersion in the perpendicular angle at a given angle

        INPUT:

           dangle - angle offset along the stream

           assumeZeroMean= (True) if True, assume that the mean is zero (should be)

           smallest= (False) calculate for smallest eigenvalue direction rather than for middle

           simple= (False), if True, return an even simpler estimate

        OUTPUT:

           dispersion in the perpendicular angle at this angle

        HISTORY:

           2013-12-06 - Written - Bovy (IAS)

        """
        if smallest: eigIndx= 0
        else: eigIndx= 1
        if simple:
            dt= self.meantdAngle(dangle,use_physical=False)
            return numpy.sqrt(self._sigangle2
                              +self._sortedSigOEig[eigIndx]*dt**2.)
        aplow= numpy.amax([numpy.sqrt(self._sortedSigOEig[eigIndx])*self._tdisrupt*5.,
                           self._sigangle])
        numsig2= integrate.quad(lambda x: x**2.*self.pangledAngle(x,dangle),
                                    aplow,-aplow)[0]
        if not assumeZeroMean:
            nummean= integrate.quad(lambda x: x*self.pangledAngle(x,dangle),
                                    aplow,-aplow)[0]
        else:
            nummean= 0.
        denom= integrate.quad(self.pangledAngle,aplow,-aplow,(dangle,))[0]
        if denom == 0.: return numpy.nan
        else: return numpy.sqrt(numsig2/denom-(nummean/denom)**2.)
NAME:

           sigangledAngle

        PURPOSE:

           calculate the dispersion in the perpendicular angle at a given angle

        INPUT:

           dangle - angle offset along the stream

           assumeZeroMean= (True) if True, assume that the mean is zero (should be)

           smallest= (False) calculate for smallest eigenvalue direction rather than for middle

           simple= (False), if True, return an even simpler estimate

        OUTPUT:

           dispersion in the perpendicular angle at this angle

        HISTORY:

           2013-12-06 - Written - Bovy (IAS)