Fig. 4

The optimal variable selection in calibration subsets by CARS and RF. a Soluble sugars. b Cellulose. c Hemicellulose. d Lignin. e Ash. f Hexoses released after pretreatment followed by enzymatic hydrolysis. g Pentoses released after pretreatment followed by enzymatic hydrolysis. h Total carbohydrates released after pretreatment followed by enzymatic hydrolysis. Log(1/R) is used to relate near-infrared reflectance to concentration of absorbing material. CARS competitive adaptive reweighted sampling, RF random frog