tdForm {BIOdry} | R Documentation |
ltd formulas
Description
This function formulates linear time-decline formulas (ltd) from categorical variables in multilevel ecological data series.
Usage
tdForm(rd, prim.cov = FALSE, on.time = TRUE, log.t = FALSE, lev.rm = NULL)
Arguments
rd |
|
prim.cov |
|
on.time |
|
log.t |
|
lev.rm |
NULL or |
Details
the ltd formulas belong to following
general equation: log (x) = log (csx) + f(time);
where the relative organic growth (x) is
explained by the cumulative organic growth (csx)
plus a function of time f(time); with f(time)
being either the time or a logarithmic
transformation the time. The ltd can be
implemented by modelFrame
function
to subtract trends in organic MEDS
Value
formula
with the forms: 'resp ~ cov | group' or '~ cov'.
Author(s)
Wilson Lara <wilarhen@gmail.com>, Felipe Bravo <fbravo@pvs.uva.es>
References
Zeide B. 1993. Analysis of Growth Equations. For. Sci., 39: 594-616.
Examples
## an ltd formula:
lev <- c('plot','tree')
tdeq <- tdForm(lev,log.t = TRUE)
tdeq
## (not run) only primary covariate:
tdeq1 <- tdForm(lev,prim.cov = TRUE)
tdeq1
##Multilevel data frame of tree-ring widths:
data(Prings05,envir = environment())
## removing two levels: 'plot' and 'tree' from the formula
tdea2 <- tdForm(Prings05, lev.rm = c('plot','tree'))
tdea2 <- tdForm(Prings05, lev.rm = 2:3)