PAE step 3: leaf area estimation. In (c) and (d), each point represents a leaf, the 95% confidence intervals are the dashed lines, and the 95% prediction intervals are the grey dotted dash lines. (a) The definition of "curvature ratio" (cr). (b) The distribution of cr in the training data. (c) The linear relationship between leaf length and leaf area if cr < 0.07. (d) The exponential relationship between leaf length and leaf area if cr ≥ 0.07.