Calculate Rubification component of Profile Development Index after Harden (1982) "A quantitative index of soil development from field descriptions: Examples from a chronosequence in central California". Accepts vectorized inputs for hue and chroma to produce vector output.

In Harden (1982) rubification is calculated relative to a reference parent material. Several other non-color components are normalized relative to a maximum value and summed to obtain the overall Profile Development Index.

harden.rubification(hue, chroma, hue_ref, chroma_ref)



A character vector containing Munsell hues (e.g. "7.5YR")


A numeric vector containing Munsell chromas


A character vector containing Munsell hue(s) (e.g. "10YR") for reference material


A numeric vector containing Munsell chroma(s) for reference material


A numeric vector reflecting horizon redness increase relative to a reference (e.g. parent) material.


Harden, J.W. (1982) A quantitative index of soil development from field descriptions: Examples from a chronosequence in central California. Geoderma. 28(1) 1-28. doi: 10.1016/0016-7061(82)90037-4


Andrew G. Brown


data("jacobs2000", package="aqp")

# LEFT JOIN hue, value, chroma matrix color columns
horizons(jacobs2000) <- cbind(horizons(jacobs2000)[,c(idname(jacobs2000), hzidname(jacobs2000))],
                              parseMunsell(jacobs2000$matrix_color_munsell, convertColors = FALSE))

#' # calculate a mixed 150-200cm color ~"parent material"
jacobs2000$c_horizon_color <- profileApply(jacobs2000, function(p) {

  # and derive the parent material from the 150-200cm interval
  p150_200 <- glom(p, 150, 200, truncate = TRUE)
  p150_200$thickness <- p150_200$bottom - p150_200$top
  # subset colors and thickness
  clrs <- na.omit(horizons(p150_200)[,c('matrix_color_munsell','thickness')])
  # simulate a subtractive mixture using thickness as weight
  w = clrs$thickness, 
  mixingMethod = 'exact')$munsell

# segment profile into 1cm slices (for proper depth weighting)
jacobs2000$rubif <- profileApply(jacobs2000, function(p) {

  # sum the melanization index over the 0-100cm interval
  p0_100 <- segment(p, 0:100)

  ccol <- parseMunsell(p$c_horizon_color, convertColors = FALSE)

    hue = p0_100$hue,
    chroma = as.numeric(p0_100$chroma),
    hue_ref = ccol$hue,
    chroma_ref = as.numeric(ccol$chroma)
  ), na.rm = TRUE)


jacobs2000$rubiforder <- order(jacobs2000$rubif)

# Plot in order of increasing Rubification index

plotSPC(jacobs2000, axis.line.offset = -1,
        color = "matrix_color",
        label = "rubif",
        plot.order = jacobs2000$rubiforder)

abline(h = c(0,100,150,200), lty = 2)

# Add [estimated] parent material color swatches
trash <- sapply(seq_along(jacobs2000$c_horizon_color), function(i) {
  rect(i - 0.15, 250, i + 0.15, 225,
       col = parseMunsell(jacobs2000$c_horizon_color[jacobs2000$rubiforder[i]]))