amod: Allometric modeling

Description Usage Arguments Details Value Author(s) Examples

Description

Parameters of simple allometric model are evaluated to derive allometric components of organisms from longitudinal variables.

Usage

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

Arguments

cs

Numeric. Sequence of mesures of an organic component.

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 variables. 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 a sequence of mesures of an organic component (e.g. the tree-radial increments). Different allometric variables can be computed; for the case of tree-radial increments, mp = c(1,1) produces diameters, and mp = c(0.25 * pi,2) computes basal areas. The 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 from tree-ring widths. A column of increments of cs (x) is also computed for further in-package modeling of relative organic growth from cumulative organic growth (see tdForm function).

Value

data.frame of computed allometric-organic components and their correspondent relative increments.

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)


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