*lemna* is a software package for the language *R*. It implements model
equations and default parameters to simulate the
toxicokinetic-toxicodynamic (TKTD) model of the *Lemna* aquatic
plant. *Lemna* is a standard test macrophyte used in ecotox
effect studies. The model was described and published by the *SETAC
Europe Interest Group Effect Modeling* (Klein *et al.* 2022).
It is a refined description of the *Lemna* TKTD model published
by Schmitt *et al.* (2013). This package contains the model’s
reference implementation which is provided by the *SETAC*
interest group.

```
## install directly from CRAN
install.packages("lemna")
## install latest development version from GitHub
#install.packages("remotes")
::install_github("nkehrein/lemna", dependencies=TRUE) remotes
```

The lemna package provides model equations and some useful helpers to
simulate the growth of *Lemna* (duckweed) aquatic plant
populations. A simulation is run by using the `lemna()`

function. The required scenario data are either supplied individually on
function call or are passed as a pre-defined scenario object, such as
the `focusd1`

sample scenario:

```
library(lemna)
# simulate sample scenario
<- lemna(focusd1)
result head(result)
#> time BM M_int C_int FrondNo
#> 1 0 80.00000 0.0000000 0.0000000000 200000.0
#> 2 1 79.48177 0.6614503 0.0004983256 198704.4
#> 3 2 79.00414 2.2061048 0.0016720907 197510.3
#> 4 3 78.57538 4.1750616 0.0031817050 196438.5
#> 5 4 78.23362 6.2899397 0.0048143381 195584.0
#> 6 5 78.01035 8.3810150 0.0064332127 195025.9
plot(result)
```

The package contains two vignettes that may help you getting started:

- Introduction
to the Lemna package

A general*Tutorial*and guide to the package functions - Lemna
model verification

A verification of the model implementation against results of the Schmitt*et al.*implementation. Contains advanced workflows of package features.

The package and its source code is free and open-source software available under the MIT license.

If you find any issues or bugs within the package, please create a new issue on GitHub.

- Klein J., Cedergreen N., Heine S., Kehrein N., Reichenberger S.,
Rendal C., Schmitt W., Hommen U., 2022: Refined description of the
*Lemna*TKTD growth model based on*Schmitt et al.*(2013) – equation system and default parameters, implementation in R. Report of the working group*Lemna*of the SETAC Europe Interest Group Effect Modeling. Version 1.1, uploaded on 09 May 2022. https://www.setac.org/group/SEIGEffectModeling - Schmitt W., Bruns E., Dollinger M., Sowig P., 2013: Mechanistic
TK/TD-model simulating the effect of growth inhibitors on
*Lemna*populations. Ecol Model 255, pp. 1-10. DOI: 10.1016/j.ecolmodel.2013.01.017