A function for detremining starting values for nonlinear parameter estimation in the water retention models

Description

This function determines the starting values for estimation of parameters in the water retention models. The input data must contain at least the x (suction potential) and y(moisture contents) variables. It gives the starting values as close to the expected estimates as possible.

Usage

1

Arguments

data

This is the water retention data with at least x (suction potential) and y(moisture contents) variables. The number of rows of the data should be at least 4 entries/levels of suction potential

Details

The data contains x columns and y columns which are used by the function. The initial x value should not be zero but something close like 0.001

Value

A vector of five values: pars[1]: thr- The residual moisture content, pars[2]: ths- The saturated moisture content, Pars[3]: alp- Inverse of air entry potential, pars[4]: nscal-index of pore-size distribution, and pars[5]: mscal-scaling parameter related to nscal

Author(s)

Christian Thine Omuto

See Also

SSvgm, Sskosugi, SSgard

Examples

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data(isric)
pf=subset(isric, Sample=="Benin3")
Dstart(pf)[1]## thr initial value