kozaklast.fx: Function to computes the stem diameter of a tree according to...

In biometrics: A Package for Biometrics and Modelling

Function to computes the stem diameter of a tree according to the Kozak (2004) taper equation.

Description

Function of the Kozak (2004) taper equation model, based upon the model parameters, and the tree variables: diameter, total height, and stem height. The mathematical expression is as follows (escribir la correcta)

d_{l_{i}} = \alpha_0d_i^{\alpha_1}\alpha_2^{d_i}X_{l_{i}}^{ \left[\beta_1z_{l_{i}}^{2}+\beta_2\ln{(z_{l_{i}} + 0,001)} + \beta_3\sqrt{z_{l_{i}}}+ \beta_4 e^{z_{l_{i}}}+\beta_5(d_i/h_i)\right] },

where: d_{l_{i}} is the stem diameter at stem-height h_{l_{i}} for the i-th tree; and d_i and h_i are the tree-level variables diameter at breast height and total height, respectively, for tje i-th tree. The other terms are

z_{l_{i}}=\frac{h_{l_{i}}}{h_i},

X_{l_{i}}=\frac{ 1-\sqrt{ z_{l_{i}}} }{ 1-\sqrt{p} },

with p being the inflextion point.

Usage

kozaklast.fx(d, h, hl, paramod)

Arguments

d	is the diameter at breast height (1.3 m) of the tree. The measurement unit is cm in the metric system, but ultimately it will depend on how the model was previously fitted, because of the measurement unit of the variables included.
h	is total height of the tree.
hl	is stem height within the tree, thus h_l \leq h.
paramod	is a vector having the nine coefficients of the taper model in the following order: \alpha_0,\alpha_1,\alpha_2,\beta_1,\beta_2,\beta_3,\beta_4,\beta_5, and \beta_6.

Value

Returns the diameter of the stem at the stem-height h_l, thus d_l, for the Kozak (1988) functional form, based upon tree diameter d and total height h.

Author(s)

Christian Salas-Eljatib.

References

Kozak A. 2004. My last words on taper equations. The Forestry Chronicle 80: 507–515. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1139/x88-213")}

Examples

# Parameters
a0<- 0.80; a1<- 0.88809; a2<- 0.2
b1<- 0.95086; b2<- -0.18090; b3<- 0.61407;
b4<- -0.35105; b5 <- 0.05686; b6 <- 0.001;
coefs<-c(a0,a1,a2,b1,b2,b3,b4,b5,b6);
# Tree attributes
dbh <- 45; toth <- 27

# Using the function
hl.int <- c(0.3, 1.3, 5)
dl.hat <- kozaklast.fx(d=dbh,h=toth,hl=hl.int,paramod=coefs)
cbind(hl.int,dl.hat)
 

biometrics documentation built on March 20, 2026, 5:09 p.m.