def get_sigmoid_parameters(self, filename='shlp_sigmoid_factors.csv'):
        """ Retrieve the sigmoid parameters from csv-files

        Parameters
        ----------
        filename : string
            name of file where sigmoid factors are stored
        """

        file = os.path.join(self.datapath, filename)
        sigmoid = pd.read_csv(file, index_col=0)
        sigmoid = sigmoid.query(
            'building_class=={0} and '.format(self.building_class) +
            'shlp_type=="{0}" and '.format(self.shlp_type) +
            'wind_impact=={0}'.format(self.wind_class))

        a = float(sigmoid['parameter_a'])
        b = float(sigmoid['parameter_b'])
        c = float(sigmoid['parameter_c'])
        if self.ww_incl:
            d = float(sigmoid['parameter_d'])
        else:
            d = 0
        return a, b, c, d
Retrieve the sigmoid parameters from csv-files

        Parameters
        ----------
        filename : string
            name of file where sigmoid factors are stored