texture: Textural conversions

In aqp: Algorithms for Quantitative Pedology

Textural conversions

Description

These functions consist of several conversions between sand, silt and clay to texture class and visa versa, textural modifiers to rock fragments, and grain size composition to the family particle size class.

Usage

texcl_to_ssc(texcl = NULL, clay = NULL, sample = FALSE)

ssc_to_texcl(
  sand = NULL,
  clay = NULL,
  simplify = FALSE,
  as.is = FALSE,
  droplevels = TRUE
)

texmod_to_fragvoltot(texmod = NULL, lieutex = NULL)

texture_to_taxpartsize(
  texcl = NULL,
  clay = NULL,
  sand = NULL,
  sandvf = NULL,
  fragvoltot = NULL
)

texture_to_texmod(texture, duplicates = "combine")

fragvol_to_texmod(
  object = NULL,
  gravel = NULL,
  cobbles = NULL,
  stones = NULL,
  boulders = NULL,
  channers = NULL,
  flagstones = NULL,
  paragravel = NULL,
  paracobbles = NULL,
  parastones = NULL,
  paraboulders = NULL,
  parachanners = NULL,
  paraflagstones = NULL,
  as.is = TRUE,
  droplevels = TRUE
)

Arguments

texcl	vector of texture classes than conform to the USDA code conventions (e.g. c|C, sil|SIL, sl|SL, cos|COS)
clay	vector of clay percentages
sample	logical: should ssc be random sampled from the lookup table? (default: FALSE)
sand	vector of sand percentages
simplify	Passed to SoilTextureLevels() to set the number of possible texture classes. If TRUE, the ordered factor has a maximum of 12 levels, if FALSE (default) the ordered factor has a maximum of 21 levels (including e.g. very fine/fine/coarse variants)
as.is	logical: should character vectors be converted to factors? (default: TRUE)
droplevels	logical: indicating whether to drop unused levels in factors. This is useful when the results have a large number of unused classes, which can waste space in tables and figures.
texmod	vector of textural modifiers that conform to the USDA code conventions (e.g. gr|GR, grv|GRV)
lieutex	vector of in lieu of texture terms that conform to the USDA code conventions (e.g. gr|GR, pg|PG), only used when fragments or artifacts are > 90 percent by volume (default: NULL))
sandvf	vector of very fine sand percentages
fragvoltot	vector of total rock fragment percentages
texture	vector of combinations of texcl, texmod, and lieutex (e.g. CL, GR-CL, CBV-S, GR)
duplicates	character: specifying how multiple values should be handled, options are "combined" (e.g. 'GR & GRV) or "max"(e.g. 'GRV')
object	data.frame: containing the following column names: gravel, cobbles, stones, boulders, channers, flagstones, paragravel, paracobbles, parastones, paraboulders, parachanners, paraflagstones
gravel	numeric: gravel volume %
cobbles	numeric: cobble volume %
stones	numeric: stone volume %
boulders	numeric: boulder volume %
channers	numeric: channer volume %
flagstones	numeric: flagstone volume %
paragravel	numeric: para gravel volume %
paracobbles	numeric: para cobble volume %
parastones	numeric: para stone volume %
paraboulders	numeric: para boulder volume %
parachanners	numeric: para channer volume %
paraflagstones	numeric: para flagstone volume %

Details

These functions are intended to estimate missing values or allocate particle size fractions to classes. The ssc_to_texcl() function uses the same logic as the particle size estimator calculation in NASIS to classify sand and clay into texture class. The results are stored in soiltexture and used by texcl_to_ssc() as a lookup table to convert texture class to sand, silt and clay. The function texcl_to_ssc() replicates the functionality described by Levi (2017). The texmod_to_fragvol() function similarly uses the logical from the Exhibit618-11_texture_modifier.xls spreadsheet to determine the textural modifier from the various combinations of rock and pararock fragments (e.g. GR and PGR).

When sample = TRUE, the results can be used to estimate within-class, marginal distributions of sand, silt, and clay fractions. It is recommended that at least 10 samples be drawn for reasonable estimates.

The function texmod_to_fragvoltot returns a data.frame with multiple fragvoltot columns differentiated by tailing abbreviations (e.g. _r) which refer to the following:

1. l = low

2. r = representative

3. h = high

4. nopf = no pararock fragments (i.e. total fragments - pararock fragments)

The function texture_to_texmod() parses texture (e.g. GR-CL) to extract the texmod values from it in the scenario where it is missing from texmod column. If multiple texmod values are present (for example in the case of stratified textures) and duplicates = "combine" they will be combined in the output (e.g. GR & CBV). Otherwise if duplicates = "max" the texmod with the highest rock fragment (e.g. CBV) will be returned.

Unlike the other functions, texture_to_taxpartsize() is intended to be computed on weighted averages within the family particle size control section. Also recall from the criteria that carbonate clay should be subtracted from clay content and added to silt content. Similarly, if the percent of very fine sand is known it should be subtracted from the sand, and added to the silt content. Unlike the other functions, texture_to_taxpartsize() is intended to be computed on weighted averages within the family particle size control section. Also recall from the criteria that carbonate clay should be subtracted from clay content and added to silt content. Similarly, if the percent of very fine sand is known it should be subtracted from the sand, and added to the silt content.

Value

• texcl_to_ssc: A data.frame containing columns "sand","silt", "clay"

• ssc_to_texcl: A character vector containing texture class

• texmod_to_fragvoltot: A data.frame containing columns "fragvoltot_l", "fragvoltot_r", "fragvoltot_h", "fragvoltot_l_nopf", "fragvoltot_r_nopf", "fragvoltot_h_nopf"

• texture_to_taxpartsize: a character vector containing "taxpartsize" classes

• texture_to_texmod: a character vector containing "texmod" classes

• texmod_to_fragvol: a data.frame containing "texmod" and "lieutex" classes

Author(s)

Stephen Roecker

References

Matthew R. Levi, Modified Centroid for Estimating Sand, Silt, and Clay from Soil Texture Class, Soil Science Society of America Journal, 2017, 81(3):578-588, ISSN 1435-0661, \Sexpr[results=rd]{tools:::Rd_expr_doi("10.2136/sssaj2016.09.0301")}.

See Also

SoilTextureLevels

hz_to_taxpartsize(), lookup_taxpartsize()

Examples

# example of ssc_to_texcl()
tex <- expand.grid(sand = 0:100, clay = 0:100)
tex <- subset(tex, (sand + clay) < 101)
tex$texcl <- ssc_to_texcl(sand = tex$sand, clay = tex$clay)
head(tex)

# example of texcl_to_ssc(texcl)
texcl <- c("cos", "s", "fs", "vfs", "lcos", "ls",
          "lfs", "lvfs", "cosl", "sl", "fsl", "vfsl", "l",
          "sil", "si", "scl", "cl", "sicl", "sc", "sic", "c"
          )
test <- texcl_to_ssc(texcl)
head(test <- cbind(texcl, test), 10)


# example of texcl_to_ssc(texcl, clay)
data(soiltexture)
st <- soiltexture$values
idx <- sample(1:length(st$texcl), 10)
st <- st[idx, ]
ssc <- texcl_to_ssc(texcl = st$texcl)
head(cbind(texcl = st$texcl, clay = ssc$clay))


# example of texmod_to_fragvoltol
frags <- c("gr", "grv", "grx", "pgr", "pgrv", "pgrx")
head(texmod_to_fragvoltot(frags))


# example of texture_to_taxpartsize()
tex <- data.frame(texcl = c("c", "cl", "l", "ls", "s"),
                  clay  = c(55, 33, 18, 6, 3),
                  sand  = c(20, 33, 42, 82, 93),
                  fragvoltot = c(35, 15, 34, 60, 91))
tex$fpsc <- texture_to_taxpartsize(texcl = tex$texcl,
                                   clay = tex$clay,
                                   sand = tex$sand,
                                   fragvoltot = tex$fragvoltot)
head(tex)


# example of texture_to_taxpartsize() with carbonate clay and very fine sand
carbclay <- rnorm(5, 2, 3)
vfs <- rnorm(5, 10, 3)
st$fpsc <- texture_to_taxpartsize(texcl = tex$texcl,
                                  clay = tex$clay - carbclay,
                                  sand = tex$sand - vfs,
                                  fragvoltot = tex$fragvoltot)
head(tex)


# example of sample = TRUE
texcl <- rep(c("cl", "sil", "sl"), 10)
ssc1 <- cbind(texcl, texcl_to_ssc(texcl = texcl, sample = FALSE))
ssc2 <- cbind(texcl, texcl_to_ssc(texcl = texcl, sample = TRUE))
ssc1$sample <- FALSE
ssc2$sample <- TRUE
ssc  <- rbind(ssc1, ssc2)
aggregate(clay ~ sample + texcl, data = ssc, summary)


# example of texture_to_texmod()
tex <- c("SL", "GR-SL", "CBV-L", "SR- GR-FS GRX-COS")
texture_to_texmod(tex)
texture_to_texmod(tex, duplicates = "max")


# example of fragvol_to_texmod()
df <- expand.grid(
  gravel  = seq(0, 100, 5), 
  cobbles = seq(0, 100, 5), 
  stones  = seq(0, 100, 5), 
  boulders = seq(0, 100, 5)
  )
df <- df[rowSums(df) < 100, ]

# data.frame input
test <- fragvol_to_texmod(df)
table(test$texmod)
table(test$lieutex)

# vector inputs
fragvol_to_texmod(gravel = 10, cobbles = 10)

aqp documentation built on Oct. 19, 2024, 5:06 p.m.