Calculate Redness Index after Hurst (1977) "Visual estimation of iron in saprolite" DOI: 10.1130/0016-7606(1977)88<174:VEOIIS>2.0.CO;2. Accepts vectorized inputs for hue, value and chroma, produces vector output.
hurst.redness(hue, value, chroma)A character vector containing Munsell hues (e.g. "7.5YR")
A numeric vector containing Munsell values
A numeric vector containing Munsell chromas
A numeric vector of horizon redness index (lower values = redder).
Hurst, V.J. (1977) Visual estimation of iron in saprolite. GSA Bulletin. 88(2): 174–176. doi: https://doi.org/10.1130/0016-7606(1977)88<174:VEOIIS>2.0.CO;2