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

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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