GcClust: Clustering geochemical data with HMC sampling

#' @title Colorado geochemical data
#'
#' @description
#' In 2006, soil samples were collected at 960 sites (1 site per 280 square
#' kilometers) throughout the state of Colorado. These samples were collected
#' from a depth of 0-15 centimeters and, following a near-total multi-acid
#' digestion, were analyzed for a suite of 44 major and trace
#' elements.
#'
#' @format
#' The organization of the data is described in the package documentation.
#'
#' @details
#' The data are from Smith and others (2010); selected summary statistics of
#' these data are presented in Ellefsen and others (2014).
#'
#' These data have been edited to make them suitable for
#' analysis. First, field sample "06co437" has been deleted because
#' it has an anomalously high copper concentration.
#' Second, elements silver (Ag), cesium (Cs), mercury (Hg),
#' tellurium (Te), and selenium (Se) have been deleted because 98\%, 77\%,
#' 69\%, 94\%, and 45\%, respectively, of the measured concentrations are below
#' the lower limit of determination. (The lower limit of determination is
#' the threshold for left-censoring.) The lower limits of determination are
#' listed in Table 1 of Smith et al., 2010.
#'
#' Third, elements antimony (Sb), arsenic (As), bismuth (Bi), cadmium (Cd),
#' indium (In), phosphorous (P), and sulfur (S) have 0.208\%, 0.417\%, 1.15\%,
#' 5.62\%, 14.1\%, 0.521\%, and 3.02\%, respectively, of the measured
#' concentrations below the lower limit of determination.
#' These left-censored concentrations were assigned concentrations equal to
#' 0.65 times their respective lower limit of determination
#' (Palarea-Albaladejo and others, 2014).
#' Finally, element concentrations were
#' scaled, as necessary, so that the units for all concentrations are "mg/kg"
#' or equivalently "ppm".
#'
#' After this editing, there are 959 field samples for which
#' 39 element concentrations are reported.
#' The locations of the field samples are specified by lattitude and longitude
#' using the WGS84 datum.
#'
#' @source \url{http://pubs.usgs.gov/ds/520/}
#'
#' @references
#' Ellefsen, K.J., Smith, D.B., Horton, J.D., 2014, A modified procedure
#' for mixture-model clustering of regional geochemical data: Applied
#' Geochemistry, vol. 51, p. 315-326,
#' doi: https://doi.org/10.1016/j.apgeochem.2014.10.011.
#'
#' Palarea-Albaladejo, J., Martin-Fernandez, J.A., Buccianti, A., 2014,
#' Compositional methods for estimating elemental concentrations below
#' the limit of detection in practice using R: Journal of Geochemical
#' Exploration, vol. 141, p. 71-77,
#' doi: https://doi.org/10.1016/j.gexplo.2013.09.003.
#'
#' Smith, D.B., Ellefsen, K.J., and Kilburn, J.E., 2010,
#' Geochemical data for Colorado soils-Results from the 2006
#' state-scale geochemical survey: U.S. Geological Survey,
#' Data Series 520, 9 p.
#'
"CoGeochemData"