def METHOD_NAME(i):
    """ compute single W[:,i] """
    # optimize beta     using qp solver from cvxopt
    FB = base.matrix(np.float64(np.dot(-self.data.T, W_hat[:,i])))
    be = solvers.qp(HB, FB, INQa, INQb, EQa, EQb)
    self.beta[i,:] = np.array(be['x']).reshape((1, self._num_samples))