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` `data.frame` or `character` vector. Multilevel ecological data series or vector of ecological factors. `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(time) = ln(time)```. Default FALSE produces a log-linear time-decline formula. `lev.rm` NULL or `character` name of the ecological factor(s) in the MEDS to be removed from the formula.

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)
```

[Package BIOdry version 0.8 Index]