func (cov_func *CovSEARD) Cov(x1 *core.Vector, x2 *core.Vector) float64 { ret := 0.0 tmp := 0.0 for key, r := range cov_func.Radiuses.Data { v1 := x1.GetValue(key) v2 := x2.GetValue(key) tmp = (v1 - v2) / r ret += tmp * tmp } ret = cov_func.Amp * math.Exp(-ret) return ret }