def init_prior(self, R):
        """initialize prior for the subject

        Returns
        -------
        TFA
            Returns the instance itself.

        """
        centers, widths = self.init_centers_widths(R)
        # update prior
        prior = np.zeros(self.K * (self.n_dim + 1))
        self.set_centers(prior, centers)
        self.set_widths(prior, widths)
        self.set_prior(prior)
        return self
initialize prior for the subject

        Returns
        -------
        TFA
            Returns the instance itself.