有兴趣可以深入了解一下海瑟矩阵http://wenku.baidu.com/link?url=-GL0-wrocaDJwVIHltd4SGaM-cS6DgHP6U7mxB6MNDoqz1RHuHc7SRa6BomLR3TLTs0qg4qP3cJ2vOcpQsFd6xOgw3hEbrXYucAi5npC31y