bi_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 Bi taper function.
bi_di(dbh, h, hi, coef)
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 seven coefficients of the Bi taper function. |
the Bi (2000) variable-form taper function is represented mathematically by the following expression
di ~ dbh * (log(sin((pi/2) * (hi/h)))/(log(sin((pi/2) * (1.3/h)))))^(b0 + b1 * sin((pi/2) * (hi/h)) + b2 * cos((3 * pi/2) * (hi/h)) + b3 * (sin((pi/2) * (hi/h))/(hi/h)) + b4 * dbh + b5 * (hi/h) * dbh^0.5 + b6 * (hi/h) * h^0.5)
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) bi <- nlsLM(di ~ taper_bi(dbh, h, hih, b0, b1, b2, b3, b4, b5, b6), data=tree_scaling, start=list(b0=1.8,b1=-0.2,b2=-0.04,b3=-0.9,b4=-0.0006,b5=0.07,b6=-.14)) coef_bi <- coef(bi) dbh <- 25 h <- 20 hi <- 15 bi_di(dbh, h, hi, coef_bi)
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