Classification of wood surfaces according to visual appearance by multivariate analysis of wood feature data

Journal of Wood Science

Official Journal of the Japan Wood Research Society

Table 6 Variables included or removed in the stepwise discriminant analysis for log-sector class 2

Step	Variables		F value	Minimum D ²	Groups discriminated
	Included	Removed	F value	Minimum D ²	Groups discriminated
1	Maximum knot size	–	71.029	4.812	1–2
2	Number of knots	–	44.332	11.205	1–2
3	Span of longitudinal knot position	–	12.476	17.198	2–3
4	Standard deviation of sound knot size	–	28.589	28.333	1–2
5	Mean Euclidean distance to first nearest neighbour	–	31.818	35.875	1–3
6	–	Span of longitudinal knot position	1.613	33.161	1–3
7	Minimum black knot size	–	24.121	78.914	1–3
8	Simpson index of knot type	–	8.231	82.337	1–2
9	Standard deviation of knot size	–	26.453	115.155	2–3
10	Minimum sound knot size	–	25.399	207.024	1–2
11	Minimum knot elongation	–	4.570	232.143	1–2
12	Standard deviation of black knot size	–	5.432	263.306	1–3
13	Number of black knots	–	25.457	405.287	1–2
14	Maximum black knot size	–	11.632	527.664	1–2

The partial F value and minimum D ² indicated for each step are the values computed in the previous step that were the basis for variable inclusion or removal. The groups that each variable separated between are given likewise, i.e. the discriminated groups were always identified in the preceding step as well