diff --git a/GPy/kern/parts/exponential.py b/GPy/kern/parts/exponential.py index d8cf76f7..ea6a0f21 100644 --- a/GPy/kern/parts/exponential.py +++ b/GPy/kern/parts/exponential.py @@ -125,3 +125,16 @@ class Exponential(Kernpart): G[i, j] = G[j, i] = integrate.quad(lambda x : L(x, i) * L(x, j), lower, upper)[0] Flower = np.array([f(lower) for f in F])[:, None] return(self.lengthscale / 2. / self.variance * G + 1. / self.variance * np.dot(Flower, Flower.T)) + + def sde(self): + """ + Return the state space representation of the covariance. + """ + F = np.array([[-1/self.lengthscale]]) + L = np.array([[1]]) + Qc = np.array([[2*self.variance/self.lengthscale]]) + H = np.array([[1]]) + Pinf = np.array([[self.variance]]) + + # TODO: return the derivatives as well + return (F, L, Qc, H, Pinf) \ No newline at end of file