Quantitative Description of Color Variation

This function computes several measures of "color variation", typically associated with soil colors described in the Munsell system, using the CIE2000 dE (dE00) color contrast metric. The resulting dE00 summaries map closely to color differences as perceived by "average human vision".

Usage

colorVariation(
  m,
  method = c("frequency", "centroid", "reference", "L1"),
  ref = NULL
)

Arguments

m: character vector of colors, described using the Munsell system e.g. c('10YR 3/3', '5YR 4/6')
method: character, one of c('frequency', 'centroid', 'reference'), see Details
ref: character, a reference color specified in the Munsell system when method = 'reference'

Value

numeric, dE00 summary of color variation along with group centroid for method = c('frequency', 'centroid', 'L1')

Details

dE00 values are computed according to method:

'frequency': relative to most frequent color in m
'centroid': relative to centroid (CIELAB coordinates) of colors specified in m
'L1': relative to L1-median (geometric median) CIELAB coordinates of colors specified in m, via Gmedian::Gmedian()
'reference': relative to color specified in ref

The L1 method is more robust to outliers in m as combined pedon centroid method.

Examples


# some brownish colors with a wild outlier
m <- c('10YR 3/3', '10YR 4/4', '10YR 4/4', '5GY 6/8')

# useful when there may be a lot of duplicates
colorVariation(m, method = 'frequency')
#> [1] 10.06968
#> attr(,"most frequent")
#> [1] "10YR 4/4"

# statistical "centroid" of colors, not robust to outliers
# result may not match any color in `m`
colorVariation(m, method = 'centroid')
#> [1] 12.92885
#> attr(,"centroid")
#> [1] "5Y 4/4"

# deviation from a known reference
colorVariation(m, method = 'reference', ref = '10YR 2/1')
#> [1] 24.34378

# L1-median (requires Gmedian package) like 'centroid'
# more robust to outliers
# result will usually be very closer to a color in `m`
# colorVariation(m, method = 'L1')