# Interactive Estimation of the Groenevelt and Grant (2004) Model Parameters

### Description

An interactive graphical adjustment of the soil water retention curve via Groenevelt and Grant (2004) formula. The nonlinear least-squares estimates can be achieved taking the graphical initial values.

### Usage

1 | ```
fitsoilwater2(theta, x, x0 = 6.653, xlab = NULL, ylab = NULL, ...)
``` |

### Arguments

`theta` |
a numeric vector containing the values of soil water content. |

`x` |
a numeric vector containing pF (pore water suction) values. See |

`x0` |
the value of pF at which the soil water content becomes zero. The default is 6.653. |

`xlab` |
a label for the x axis; if is NULL, the label "pF" is used. |

`ylab` |
a label for the y axis; if is NULL, the label "Soil water content" is used. |

`...` |
further graphical arguments; see |

### Value

A plot of `theta`

versus `x`

and the curve of the current fitted model
according to the adjusted parameters in an external interactive panel.
Pressing the button "NLS estimates" a `nls`

summary of the
fitted model is printed on console whether convergence is achieved, otherwise
a warning box of "No convergence" is shown.

### Author(s)

Anderson Rodrigo da Silva <anderson.agro@hotmail.com>

### References

Groenevelt & Grant (2004). A newmodel for the soil-water retention curve that solves the problem
of residualwater contents. *European Journal of Soil Science*, 55:479-485.

### See Also

`nls`

, `soilwater2`

, `soilwater`

### Examples

1 2 3 4 5 | ```
w <- c(0.417, 0.354, 0.117, 0.048, 0.029, 0.017, 0.007, 0)
pF <- 0:7
fitsoilwater2(w, pF)
# End (not run)
``` |