Allometric modeling

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Description

Parameters in simple allometric model are evaluated on tree radial increments to compute diameters, basal areas, tree biomasses, etc.

Usage

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amod(cs, mp = c(0.5, 1), un = NULL)

Arguments

cs

Numeric vector of scaled-cummulative sums such as that produced by scacum.

mp

Numeric. vector with allometric parameters. Default c(0.5,1) maintains the original radii (see details for other variables)

un

NULL, or bidimensional character vector to transform SI units of the processed variable. The SI units can be expressed in micrometers 'mmm', milimeters 'mm', centimeters 'cm', decimeters 'dm', or meters 'm'. If NULL then original units are maintained.

Details

The simple allometric model has the form: a * cs ^ b, with a,b being constants in mp, and cs being scaled-cummulative sums. Different dendrometric variables can be computed; for example, c(1,1) produces diameters, and c(0.25 * pi,2) computes basal areas. Argument mp can have more than two parameters: c(a1,b1,a2,b2, ..., an,bn), with n being the number of times that allometric model will be recursively implemented. Such recursive evaluation is useful to derive variables which depend on other allometric covariables: i.e allometric model would be implemented twice to recursively compute diameters and tree biomasses. A column of increments of cs (x) is also computed by implementing setdiff.

Value

data.frame object.

Author(s)

Wilson Lara <wilarhen@gmail.com>, Felipe Bravo <fbravo@pvs.uva.es>

Examples

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## radial increments
set.seed(1)
w <- abs(rnorm(12,1,1))
names(w) <- 1951:1962
## scaled and cummulative radial increments
sr <- scacum(w)
## diameters
d <- amod(sr[,2],c(1,1))
## basal areas (m2):
ba <- amod(sr[,2],c(0.25 * pi,2),c('mm','m'))
print(ba)