This function calculates maximum moving window time weighted average
concentrations (TWAs) for kinetic models fitted with `mkinfit`

.
Currently, only calculations for the parent are implemented for the SFO,
FOMC, DFOP and HS models, using the analytical formulas given in the PEC
soil section of the FOCUS guidance.

```
max_twa_parent(fit, windows)
max_twa_sfo(M0 = 1, k, t)
max_twa_fomc(M0 = 1, alpha, beta, t)
max_twa_dfop(M0 = 1, k1, k2, g, t)
max_twa_hs(M0 = 1, k1, k2, tb, t)
```

## Arguments

- fit
An object of class `mkinfit`

.

- windows
The width of the time windows for which the TWAs should be
calculated.

- M0
The initial concentration for which the maximum time weighted
average over the decline curve should be calculated. The default is to use
a value of 1, which means that a relative maximum time weighted average
factor (f_twa) is calculated.

- k
The rate constant in the case of SFO kinetics.

- t
The width of the time window.

- alpha
Parameter of the FOMC model.

- beta
Parameter of the FOMC model.

- k1
The first rate constant of the DFOP or the HS kinetics.

- k2
The second rate constant of the DFOP or the HS kinetics.

- g
Parameter of the DFOP model.

- tb
Parameter of the HS model.

## Value

For `max_twa_parent`

, a numeric vector, named using the
`windows`

argument. For the other functions, a numeric vector of
length one (also known as 'a number').

## References

FOCUS (2006) “Guidance Document on Estimating Persistence
and Degradation Kinetics from Environmental Fate Studies on Pesticides in
EU Registration” Report of the FOCUS Work Group on Degradation Kinetics,
EC Document Reference Sanco/10058/2005 version 2.0, 434 pp,
http://esdac.jrc.ec.europa.eu/projects/degradation-kinetics

## Examples

```
fit <- mkinfit("FOMC", FOCUS_2006_C, quiet = TRUE)
max_twa_parent(fit, c(7, 21))
#> 7 21
#> 34.71343 18.22124
```