metrics2Vol: Tree volumes in NFI data
In basifoR: Retrieval and Processing of the Spanish National Forest Inventory

Description Usage Arguments Details Value Author(s) Examples

This function computes over bark volumes ('m3') processing tree metrics from databases of the SNFI data and using volume equations established in 2nd NFI, see Details section. To derive dendrometric summaries use dendroMetrics.

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metrics2Vol(nfi, cub.met = "freq", 
    keep.var = FALSE, 
    ...)

`nfi`	`character` or `data.frame`. URL/path to a compressed file of the NFI (.zip) having data of either .dbf or .mdb file extensions; or data frame such as that produced by `nfiMetrics`; or data frame such as that produced by `readNFI`.
`cub.met`	`character`. Cubication method. Default `'freq'` implements the equation form that most frequently match the data, see `details` section. Additional methods have not yet been implemented.
`keep.var`	`logical`. Keep the variables used to compute the volumes. Default `FALSE`.
`...`	Depending on `'nfi'`, additional arguments in `metrics2Vol` or `nfiMetrics` or `readNFI`.

The quations from the second SNFI used have the forms 'v ~ par1 + par2 * (d^2) * h', and 'v ~ par1 * (d^par2) * (h^par3)'. These equations estimate over bark volumes in 'dcm3' but the function transform the units so the output volumes have 'm3' units. The function assign equation forms and parameters depending on several variables, including the provincial unit, the tree species, the tree diameter, and the tree height. Consequently, objects from nfiMetrics must have these variables.

data.frame. Depending on keep.var, short or expanded data set. Short data sets contain the volumes v ('m3') plus the metrics defined in nfiMetrics. The expanded data contains additional columns with the variables used to compute the volumes.

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

madridNFI <- system.file("ifn3p28_tcm30-293962.zip", package="basifoR")
rmad <- readNFI(madridNFI)[1:10,]
vmad <- metrics2Vol(rmad)
head(vmad)
## see metric units
attr(vmad,'units')