def getVCF(SM0, SM1, SM2):
    """This function evaluate the variance of the central freuency of the PSD.::
            
            VCF = (1 / SM0)*sum(Pj*(fj - fc)**2),j = 1 --> M, = SM2 / SM0 - (SM1 /SM0) **2
        
        * Input:
            * SM0: spectral moment of order 0
            * SM1: spectral moment of order 1
            * SM2: spectral moment of order 0
        * Output: 
            * Variance of Central frequency of the Power spectrum
            
        :param SM0: Spectral moment of order 0
        :type SM0: float
        :param SM1: Spectral moment of order 1
        :type SM1: float
        :param SM2: Spectral moment of order 2
        :type SM2: float
        :return: Variance of central frequency
        :rtype: float
    """
    VCF = SM2 / SM0 - (SM1 / SM0) ** 2
    return VCF
