taperpoly.fx: Carrasco polynomial function

In biometrics: A Package for Biometrics and Modelling

Carrasco polynomial function

Description

Polynomial function of Carrasco (1986)

Usage

taperpoly.fx(hl = hl, hcc = hcc, paramod = paramod, n = (length(paramod) - 1))

Arguments

hl	is stem height within the tree, thus h_l \leq h.
hcc	is height to crown base.
paramod	is a vector having the coefficients of the taper model in the following order up to n: \beta_0, \beta_1, \beta_2, ... , \beta_n
n	degree of the polynomic function

Details

This function takes the form of

\frac{d_{l_{i}}}{d_i} = \beta_0 + \beta_1 X + \beta_2 X^2 + \beta_3 X^3 + \cdots + \beta_n X^{n},

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

X = \frac{hcc_i - h_{l_i}}{hcc_i - 1.3},

Value

Returns the diameter of the stem at the stem-height h_l, thus d_l, divided by the diameter at breast height (1.3). This is

\frac{d_{l_i}}{d_i}

Author(s)

Christian Salas-Eljatib and Nicolás Campos

References

• Carrasco, J. 1986. Estudio Comparativo de dos Métodos para Evaluar la Calidad a árboles en pie y para representar la Forma del Fuste en el Bosque Siempreverde valdiviano. Tesis Ingeniero Forestal. Universidad Austral de Chile. Valdivia, Chile. 117 p.

Examples

dl <- seq(40, 0, -5)
hl <- seq(0, 16, 2)
d <- 30
hcc <- 12
h <- max(hl)
df <- data.frame(dl = dl,
                 hl = hl,
                 d = d,
                 hcc = hcc,
                 h = h)
df

myparams <- c(0.3, 0.8, 0.00003)

taperpoly.fx(hl = df$hl, hcc = df$hcc, paramod = myparams, n = 2)

df$y <- taperpoly.fx(hl = df$hl, hcc = df$hcc, paramod = myparams, n = 2)
## the n parameter is not necesary
df$y2 <- taperpoly.fx(hl = df$hl, hcc = df$hcc, paramod = myparams)
df$dl.h <- df$y * df$d
df

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