Description Usage Arguments Value Author(s) References See Also Examples
Function to self start the nonlinear Busscher's (1990) model for penetration
resistance, i.e., Pr = b0 * (θ ^ {b1}) * (Bd ^ {b2}). It creates initial
estimates (by log-linearization) of the parameters b0, b1 and b2 and uses them
to provide its least-squares estimates through nls
.
1 | fitbusscher(Pr, theta, Bd, ...)
|
Pr |
a numeric vector containing penetration resistance values. |
theta |
a numeric vector containing soil moisture values at which to evaluate the model. |
Bd |
a numeric vector containing bulk density values at which to evaluate the model. |
... |
further arguments to |
A nls
output (see help(nls)
).
Anderson Rodrigo da Silva <anderson.agro@hotmail.com>
Busscher, W. J. (1990). Adjustment of flat-tipped penetrometer resistance data to common water content. Transactions of the ASAE, 3:519-524.
fitlbc
, nls
, summary.nls
,
predict.nls
, Rsq
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | data(compaction)
attach(compaction)
out <- fitbusscher(Pr = PR, theta = Mois, Bd = BD)
summary(out)
Rsq(out)
# 3D plot
X <- seq(min(Mois), max(Mois), len = 30) # theta
Y <- seq(min(BD), max(BD), len = 30) # Bd
f <- function(x, y) coef(out)[1] * (x^coef(out)[2]) * (y^coef(out)[3])
Z <- outer(X, Y, f)
persp(X, Y, Z,
xlab = "Soil moisture",
ylab = "Soil bulk density",
zlab = "Penetration resistance",
ticktype = "detailed",
phi = 20, theta = 30)
# End (not run)
|
Loading required package: rpanel
Loading required package: tcltk
Package `rpanel', version 1.1-4: type help(rpanel) for summary information
Loading required package: MASS
Loading required package: tkrplot
---
soilphysics version 3.1
Warning messages:
1: no DISPLAY variable so Tk is not available
2: loading Rplot failed
Formula: Pr ~ b0 * (theta^b1) * (Bd^b2)
Parameters:
Estimate Std. Error t value Pr(>|t|)
b0 1.1680 0.2618 4.461 5.07e-05 ***
b1 -0.8770 0.2247 -3.903 0.000302 ***
b2 0.1105 0.5399 0.205 0.838741
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Residual standard error: 0.5579 on 47 degrees of freedom
Number of iterations to convergence: 6
Achieved convergence tolerance: 2.675e-06
$pseudo.R.squared
[1] 0.8961571
$adj.R.squared
[1] 0.8917383
attr(,"class")
[1] "Rsq"
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