BIOdry (version 0.3)

tdForm: Time-decline formula

Description

LME formulas of type time-decline (td) or log-time-decline (ltd).

Usage

tdForm(rd, prim.cov = FALSE, on.time = TRUE, log.t = FALSE, lev.rm = NULL)

Arguments

rd

data.frame object with factor-level columns, or character vector with names of factor-level columns which are decreasingly ordered.

prim.cov

logical. Print a primary covariate form: '~ cov'. If FALSE then a complete formula: 'resp ~ cov | group' is printed.

on.time

logical. If TRUE then t = 'time' (see rtimes). If FALSE then t = 'year'.

log.t

logical. If TRUE then f(t) = ln(t). Default FALSE produces a td form

lev.rm

NULL or character name of the factor-level column to be removed from the formula.

Value

with the forms: 'resp ~ cov | group' or '~ cov'.

Details

(L)td formulas belongs to general equation: log (cs) = log (x) + f(t); where the cummulative radial increments (cs) are explained by the observed radial increments (x) plus a function of time f(t); with f(t) being either the time or a logarithmic transformation the time (ltd).

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