is maximized (thereby, d ist the vector dimensionality, 1 < d < 6). The R 2 value ranges from 0 to 1, representing poor (R 2 → 0) and perfect linearity (R 2 = 1). 𝑦𝑦 𝑖𝑖 and 𝑦𝑦 � are the 𝑖𝑖th observation and mean value of y, respectively. 𝑓𝑓 𝑖𝑖 is the predicted value from the best linear fit between the 𝑚𝑚 × 1 vector 𝒙𝒙 = 𝑿𝑿𝒘𝒘 and the 𝑚𝑚 × 1 vector 𝒚𝒚. 𝒙𝒙 is the weighted sum of elements in 𝑿𝑿, with weights 𝒘𝒘.