利用最小二乘法进行拟合多元非线性方程，现代信号处理中谱估计在matlab中的使用，比较了软阈值，硬阈值及当今各种阈值计算方法。- Multivariate least squares fitting method of nonlinear equations, Modern signal processing used in the spectral estimation in matlab, Comparison of soft threshold and hard threshold and