Processed spectrum (data), FMLR reconstruction (model), and residual of the aromatic (A) and polysaccharide (B) region of the 2D 1H–13C HSQC for a wild-type sample of Arabidopsis . The color of a contour is assigned to the color of the ROI associated with the dominant signal in that region. As can be seen in the figure, a minimal number of reconstructed signals is required to yield a model with an associated residual that is less than the noise floor (noise floor = 3.0 SD). The set of contours near (3.6, 76) ppm and (4.7, 63) ppm in (B) are not reflective of poor modeling but are a consequence of the fact that no ROI was defined near those positions. Signals in that region of the spectrum were simply not modeled.