最近参考一篇外文上面做出了正常人与病人的唾液红外光谱图,用FSD进行分析。不知道这图中的difference spectrum怎么做出来的,求各位大神赐教,附上文献原图。原文描述:Figure 3 General features of FSD-processed mean IR spectra of control and diabetes (bottom) subjects and the difference spectrum(diabetes minus control, top).请各位大神赐教,怎样找出两个光谱图间的差异,怎样分析,不胜感激