random_profile: Random Profile

In ncss-tech/aqp: Algorithms for Quantitative Pedology

Random Profile

Description

Generate a random soil profile according to set criteria, with correlated depth trends.

The random walk method produces profiles with considerable variation between horizons and is based on values from the normal distribution seeded with means and standard deviations drawn from the uniform distribution of [0, 10].

The logistic power peak (LPP) function can be used to generate random soil property depth functions that are sharply peaked. LPP parameters can be hard-coded using the optional arguments: "lpp.a", "lpp.b", "lpp.u", "lpp.d", "lpp.e". Amplitude of the peak is controlled by ("lpp.a + "lpp.b"), depth of the peak by "lpp.u", and abruptness by "lpp.d" and "lpp.e". Further description of the method is outlined in (Brenton et al, 2011). Simulated horizon distinctness codes are based on the USDA-NCSS field description methods. Simulated distinctness codes are constrained according to horizon thickness, i.e. a gradual boundary (+/- 5cm) will not be simulated for horizons that are thinner than 3x this vertical distance

Usage

random_profile(
  id,
  n = c(3, 4, 5, 6),
  min_thick = 5,
  max_thick = 30,
  n_prop = 5,
  exact = FALSE,
  method = "random_walk",
  HzDistinctSim = FALSE,
  SPC = FALSE,
  ...
)

Arguments

id	a character or numeric id used for this profile
n	vector of possible number of horizons, or the exact number of horizons (see below)
min_thick	minimum thickness criteria for a simulated horizon
max_thick	maximum thickness criteria for a simulated horizon
n_prop	number of simulated soil properties (columns in the returned dataframe)
exact	should the exact number of requested horizons be generated? (defaults to FALSE)
method	named method used to synthesize depth function ('random_walk' or 'LPP'), see details
HzDistinctSim	optionally simulate horizon boundary distinctness codes
SPC	result is a SoilProfileCollection object, otherwise a data.frame object
...	additional parameters passed-in to the LPP (.lpp) function

Value

A data.frame or SoilProfileCollection object.

Note

See examples for ideas on simulating several profiles at once.

Author(s)

Dylan E. Beaudette

References

Myers, D. B.; Kitchen, N. R.; Sudduth, K. A.; Miles, R. J.; Sadler, E. J. & Grunwald, S. Peak functions for modeling high resolution soil profile data Geoderma, 2011, 166, 74-83.

See Also

profile_compare, hzDistinctnessCodeToOffset

Examples

# generate 10 random profiles, result is a list of SoilProfileCollection objects
d <- lapply(1:10, random_profile, SPC=TRUE)

# combine
d <- combine(d)

# plot
opar <- par(mar=c(0,0,3,2))
plotSPC(d, color='p1', name='name', cex.names=0.75)
par(opar)

# simulate horizon boundary distinctness codes:
d <- lapply(1:10, random_profile, SPC=TRUE, HzDistinctSim=TRUE)
d <- combine(d)

d$HzD <- hzDistinctnessCodeToOffset(d$HzDistinctCode)

opar <- par(mar=c(0,0,3,2))
plotSPC(d, name='name', color='p1', hz.distinctness.offset='HzD')
par(opar)


# depth functions are generated using the LPP function
opar <- par(mfrow=c(2,1), mar=c(0,0,3,0))

# generate data
d.1 <- lapply(1:10, random_profile, SPC=TRUE, n=c(6, 7, 8), n_prop=1, method='LPP')
d.1 <- combine(d.1)

# plot
plotSPC(d.1, name='name', color='p1', col.label = 'LPP Defaults')


# do this again, this time set all of the LPP parameters
d.2 <- lapply(1:10, random_profile, SPC=TRUE, n=c(6, 7, 8), n_prop=1, method='LPP',
           lpp.a=5, lpp.b=10, lpp.d=5, lpp.e=5, lpp.u=25)
d.2 <- combine(d.2)

# plot
plotSPC(d.2, name='name', color='p1', col.label = 'Custom LPP Parameters')


# reset plotting defaults
par(opar)



# try plotting the LPP-derived simulated data
# aggregated over all profiles
a <- slab(d.2, fm= ~ p1)
a$mid <- with(a, (top + bottom) / 2)

library(lattice)
(p1 <- xyplot(mid ~ p.q50, data=a,
              lower=a$p.q25, upper=a$p.q75, ylim=c(150,-5), alpha=0.5,
              panel=panel.depth_function, prepanel=prepanel.depth_function,
              cf=a$contributing_fraction, xlab='Simulated Data', ylab='Depth',
              main='LPP(a=5, b=10, d=5, e=5, u=25)',
              par.settings=list(superpose.line=list(col='black', lwd=2))
))

# optionally add original data as step-functions
if(require(latticeExtra)) {
  h <- horizons(d.2)
  p1 + as.layer(xyplot(top ~ p1, groups=id, data=h,
                       horizontal=TRUE, type='S',
                       par.settings=list(superpose.line=list(col='blue', lwd=1, lty=2))))
}

ncss-tech/aqp documentation built on April 19, 2024, 5:38 p.m.