Matlab双谱分析，高阶累积量的定阶，用相邻奇异值差最大定阶，绘制双谱（等高线图，双谱图，相位图，切片图）-Matlab double spectral analysis, fixed-order cumulant, with the largest difference between adjacent fixed-order singular value, drawing double spectrum (contour maps, dual spectra, phase diagram, slices)