Fig. 2

Classification of the medicinal plant samples (52 samples including 23 reference samples (red color) and 29 test samples) according to hierarchical clustering analysis (HCA) with Ward’s method as the amalgamation rule and 1-Pearson r clustering distance measurement using data from original spectra; a spectral range 200–800 nm; b spectral range 400–800 nm; c spectral range 200–400 nm