能登地方アテ丸太材の末口径とm_3あたり価格の関係曲線の検討

The auther proposed new regression models for the small end diameter-price per m3 of Ate (Thujopsis dolabrata SIEB. et ZUCC var. hondai MAKINO) logs, and examined thier applicability. In general, rising with diameter increasing, the price of logs is high within a certain diameter range that is suitable for a pillar use. This pricediameter relation can be expressed by the regression model with one peak which mathematical expression is

p = f(d) + a + bd

where p is a log price per m3, d is a top end diameter, f(d) is a peak function and a, b are constants. Following two types functions were proposed for the peak function.

GAUSS type f_G(d) = h exp [-(log2)(<(d-u)/w>^2)]

LORENZ type f_L(d) = f_L(d) = h/(1+<((d-u)/w)^2>)

where d is a small end h, u, w are constats.
The applicability of these models was examined by appled them to five observed price-diameter relationships of Ate at Noto district, Ishikawa. These regression models shown better fits and reliablity than the following ordinary eqution

p = a_0 + a_1d + a_2d^3 + a_3d^3 + a_4d^4

where p is a log price per m3, d is a small end diameter and a_0, a_1, a_2, a_3, a_4 are constants.