SScamp {HydroMe}R Documentation

A selfstarting function for estimating hydraulic parameters in the Campbell model

Description

This selfstarting model evaluates the Campbells water retention function and its parameters. It has an initial attribute that evaluates initial estimates of the parameters Ths, alp, and scal for a given set of data

Usage

SScamp(input, Ths, alp, scal)

Arguments

input numeric vector of natural logarithm of suction potential values at which to evaluate the model
Ths a numeric parameter representing the saturated moisture content when suction potential is zero
alp a numeric parameter representing the inverse of air-entry potential
scal a numeric parameter representing the slope of the water retention curve. It is related to pore-size distribution index

Details

Campbell function is a three-parameter model that does not assume the residual moisture content. The function estimates the parameters in two parts: when the product of alp and input is less than or eaual to unity and when this quantity is geater than unity

Value

a numeric vector of the same length as input.It is the value of the Campbells expression Ths*(alp*input)^(-scal) . It represents the fitted estimates of moisture contents using the Campbell function

Author(s)

Omuto, Christian Thine

See Also

SSgard, SSbrook, SSvan

Examples

##---- use part of the Wret data ---- 
data(Wret)
nWret=nrow(Wret) # gets the number of rows need (there are 232 all together) 
testW13 <-Wret[(nWret-231):(nWret-208), ] # choose the first 3 sets 
Campbel.nls <-nls(y~SScamp(lnx, Ths, alp, scal), testW13) 
Campbel.nlis <-nlsList(y~SScamp(lnx, Ths, alp, scal)|Points, testW13) 
Campbel.nlme <-nlme(Campbel.nlis) # Estimate mixed-effects

[Package HydroMe version 1.0 Index]