SSMgg {HydroMe}R Documentation

A new function based on the biexponential model to estimate soil hydraulic paremeters of water retention

Description

This selfstarting function estimates the water retention hydraulic parameters contained in the new biexponential function. It has an initial attribute that creates initial estimates of the parameters Ths1, alp1, Ths2, and alp1

Usage

SSMgg(input, Ths1, alp1, Ths2, alp2)

Arguments

input A numeric vector of the suction potentials
Ths1 A numeric parameter representing the saturated moisture content in the structural pore-space (macropores)
alp1 A numeric parameter representing the inverse of air-entry potential in the structural component
Ths2 A numeric parameter representing the saturated moisture content in the textural pore-space (micropores)
alp2 A numeric parameter representing the inverse of air-entry potential in the textural component

Value

numeric vector of the same length as input. It is the value of the expression Ths1*exp(-exp(alp1)*input) + Ths2*exp(-exp(alp2)*input) . It represents the fitted estimates of moisture using the new biexponential model

Note

Note that the parameters representing the inverse of air-entry potentials are log-transformed. These coeficients need to be back-transformed using exponential function

Author(s)

Omuto, Christian Thine

References

Groenevelt, P.H. and Grant, C.D., 2004 A new model for the soil-water retention curve that solves the problem of residual water contents European J.ournal of Soil Science, 55, 479-485

See Also

SSvan, SSbrook, SScamp

Examples

##---- Load isric data----
data(isric)
nbiexp.nls <-nls(y~SSMgg(x, Ths1, alp1, Ths2, alp2), data=isric)
plot(nbiexp.nls, Country~resid(.), abline=0) # to observe effect of geographic locations

[Package HydroMe version 1.0 Index]