kozak_di | R Documentation |
Estimates the diameter at a given height of a tree from the diameter at breast height, total height and the coefficients of the Kozak (2004) taper function.
kozak_di(dbh, h, hi, coef, p)
dbh |
tree diameter at breast height, in centimeters. |
h |
total tree height, in meters. |
hi |
height at which the diameter will be calculated, in meters. |
coef |
numerical vector containing nine coefficients of the Kozak taper function. |
p |
numerical value representing the first inflection point calculated in the segmented model of Max and Burkhart (1976). |
the Kozak (2004) variable-form taper function is represented mathematically by the following expression
di ~b0*(dbh^b1)(h^b2)((1-(hi/h)^(1/4))/(1-(p^(1/3))))^(b3*(hi/h)^4+b4*(1/exp(dbh/h))+b5*((1-(hi/h)^(1/4))/(1-(p^(1/3))))^0.1+b6*(1/dbh)+b7*(h^(1-(hi/h)^(1/3)))+b8*((1-(hi/h)^(1/4))/(1-(p^(1/3)))))
a numeric value indicating the diameter at the given height.
library(dplyr) library(minpack.lm) library(timbeR) tree_scaling <- tree_scaling %>% mutate(did = di/dbh, hih = hi/h) kozak <- nlsLM(di ~ taper_kozak(dbh, h, hih, b0, b1, b2, b3, b4, b5, b6, b7, b8, p), start=list(b0=1.00,b1=.97,b2=.03,b3=.49,b4=- 0.87,b5=0.50,b6=3.88,b7=0.03,b8=-0.19, p = .1), data = tree_scaling, control = nls.lm.control(maxiter = 1000, maxfev = 2000) ) coef_kozak <- coef(kozak)[-10] p_kozak <- coef(kozak)[10] h <- 20 dbh <- 25 di <- 5 kozak_di(dbh, h, di, coef_kozak, p_kozak)
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