Starting values for optimization functions

This functions helps to determine initial values for a selected boundary line model when using the functions blbin(), blqr(), bolides(), cbvn() and ble_profile() to determine model parameters.

Usage

startValues(model = "explore", p = NULL, digits = 2, ...)

Arguments

model: Selects the functional form of the boundary line. It includes "blm" for linear model, "lp" for linear plateau model, "mit" for the Mitscherlich model, "schmidt" for the Schmidt model, "logistic" for logistic model, "logisticND" for logistic model proposed by Nelder (1961), "inv-logistic" for the inverse logistic model, "double-logistic" for the double logistic model, "qd" for quadratic model, "trapezium" for the trapezium model and "explore" for function use exploration. The default is "explore".
p: The number of selected points used to obtain start values for the logistic mitcherlich and schmidt models. It is NULL for other models.
digits: Number of decimal points for logistic type models (default is 2).
...: Additional graphical parameters. Applies to the logistic, mitcherlich and schmidt models to control the text on the plot.

Value

A list containing the parameters of the suggested model.

Details

This function uses the locator() function. Once the model is selected, the points that make up the boundary points are selected using mouse click on the plots.

References

Fekedulegn, D., Mac Siurtain, M.P., & Colbert, J.J. 1999. Parameter estimation of nonlinear growth models in forestry. Silva Fennica 33(4): 327–336.

Lark, R. M., & Milne, A. E. (2016). Boundary line analysis of the effect of water filled pore space on nitrous oxide emission from cores of arable soil. European Journal of Soil Science, 67 , 148-159.

Author

Chawezi Miti <chawezi.miti@nottingham.ac.uk>

Examples

startValues(model="explore")
#> y = f(P₁,P₂|x)
#> 
#> $Param1
#> P₁ 
#>  0 
#> 
#> $Param2
#> P₂ 
#>  0 
#>