Application of Grey Relational Analysis and Multiple Linear Regression to Establish the Cutting Force Model of Oil Peony Stalk

Table 6

Model result of different methods.

Methods	Calibration model			Prediction model
	Relational expression		RMSEC		RMSEP
PLSR	y = 2.042 + 4.519x^1 + 0.117x^2 + 6.320x^3 + 13.423x^4 + 0.177x^5 + 4.740x^6 − 8.366x^7 − 15.807x^8 + 0.631x^9 + 1.683x^10 − 0.575x^11	0.773	3.499	0.720	5.885
PCA + MLR	y = −44.887 + 17.267x^1 + 0.507x^2 + 55.341x^3 − 135.052x^4  + 0.115x^5 + 4.661x^6	0.793	2.750	0.701	6.079
GRA (0.5) + MLR	y = −112.601 + 0.579x^2 − 0.244x^5 + 2.562x^9 + 5.677x^10 + 0.277x^11	0.801	2.862	0.820	4.715
GRA (0.7) + MLR	y = −25.805 + 0.536x^2 + 1.030x^5	0.630	2.872	0.900	3.518