fitsoilwater5 | R Documentation |
An interactive graphical adjustment of the soil water retention curve via the van Genuchten's formula, modified by Pierson and Mulla (1989). The nonlinear least-squares estimates can be achieved taking the graphical initial values. It may be useful to estimate the parameters needed in the high-energy-moisture-characteristics (HEMC) method, which is used to analyze the aggregate stability.
fitsoilwater5(theta, x, theta_S, xlab = NULL, ylab = NULL, ...)
theta |
a numeric vector containing the values of soil water content. |
x |
a numeric vector containing the matric potential values. |
theta_S |
an offset; a value for the parameter |
xlab |
a label for the x axis; if is NULL, the label "Matric potential" is used. |
ylab |
a label for the y axis; if is NULL, the label "Soil water content" is used. |
... |
further graphical arguments; see |
The parameter theta_S must be passed as an argument. It is recommended to consider it as the highest water content value in the data set or the water content at saturation.
A plot of theta
versus x
and the curve of the current fitted model
according to the adjusted parameters in an external interactive panel.
Pressing the button "NLS estimates" a nls
summary of the
fitted model is printed on console whether convergence is achieved, otherwise
a warning box of "No convergence" is shown.
Anderson Rodrigo da Silva <anderson.agro@hotmail.com>
Pierson, F.B.; Mulla, D.J. (1989) An Improved Method for Measuring Aggregate Stability of a Weakly Aggregated Loessial Soil. Soil Sci. Soc. Am. J., 53:1825–1831.
nls
, soilwater5
h <- seq(0.1, 40, by = 2) w <- c(0.735, 0.668, 0.635, 0.612, 0.559, 0.462, 0.369, 0.319, 0.296, 0.282, 0.269, 0.256, 0.249, 0.246, 0.239, 0.236, 0.229, 0.229, 0.226, 0.222) plot(w ~ h) # suggestions of starting values: thetaR = 0.35, alpha = 0.1, n = 10, # b0 = 0.02, b1 = -0.0057, b2 = 0.00004 (Not run) fitsoilwater5(theta = w, x = h, theta_S = 0.70) # End (Not run)
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