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Estimates the Mean Ceramic Date of an assemblage.

Usage

mcd(object, dates, ...)

# S4 method for numeric,numeric
mcd(object, dates, na.rm = FALSE)

# S4 method for CountMatrix,numeric
mcd(object, dates)

# S4 method for MeanDate
bootstrap(
  object,
  level = 0.95,
  type = c("student", "normal"),
  probs = c(0.25, 0.5, 0.75),
  n = 1000
)

# S4 method for MeanDate
jackknife(object)

Arguments

object

A numeric vector, a arkhe::CountMatrix or a MeanDate object.

dates

A numeric vector of dates.

...

Currently not used.

na.rm

A logical scalar: should missing values (including NaN) be removed?

level

A length-one numeric vector giving the confidence level. Must be a single number between \(0\) and \(1\). If NULL, no confidence interval are computed.

type

A character string giving the type of confidence interval to be returned. It must be one "student" (default) or "normal". Any unambiguous substring can be given. Only used if level is not NULL.``

probs

A numeric vector of probabilities with values in \([0,1]\) (see stats::quantile()). If NULL, quantiles are not computed.

n

A non-negative integer giving the number of bootstrap replications.

Value

Details

The Mean Ceramic Date (MCD) is a point estimate of the occupation of an archaeological site (South 1977). The MCD is estimated as the weighted mean of the date midpoints of the ceramic types (based on absolute dates or the known production interval) found in a given assemblage. The weights are the relative frequencies of the respective types in the assemblage.

A bootstrapping procedure is used to estimate the confidence interval of a given MCD. For each assemblage, a large number of new bootstrap replicates is created, with the same sample size, by resampling the original assemblage with replacement. MCDs are calculated for each replicates and upper and lower boundaries of the confidence interval associated with each MCD are then returned.

References

South, S. A. (1977). Method and Theory in Historical Archaeology. New York: Academic Press.

See also

plot_mcd

Other dating methods: event()

Author

N. Frerebeau

Examples

## Mean Ceramic Date
## Coerce the zuni dataset to an abundance (count) matrix
data("zuni", package = "folio")
counts <- as_count(zuni)

## Set the start and end dates for each ceramic type
dates <- list(
  LINO = c(600, 875), KIAT = c(850, 950), RED = c(900, 1050),
  GALL = c(1025, 1125), ESC = c(1050, 1150), PUBW = c(1050, 1150),
  RES = c(1000, 1200), TULA = c(1175, 1300), PINE = c(1275, 1350),
  PUBR = c(1000, 1200), WING = c(1100, 1200), WIPO = c(1125, 1225),
  SJ = c(1200, 1300), LSJ = c(1250, 1300), SPR = c(1250, 1300),
  PINER = c(1275, 1325), HESH = c(1275, 1450), KWAK = c(1275, 1450)
)

## Calculate date midpoints
mid <- vapply(X = dates, FUN = mean, FUN.VALUE = numeric(1))

## Calculate MCD
mc_dates <- mcd(counts, dates = mid)
head(mc_dates)
#> LZ1105 LZ1103 LZ1100 LZ1099 LZ1097 LZ1096 
#>   1162   1138   1154   1091   1092    841 

## Plot
plot(mc_dates, select = 100:125)


## Bootstrap resampling
boot <- bootstrap(mc_dates, n = 30)
head(boot)
#>         min      mean  max     lower     upper     Q25    Q50     Q75
#> LZ1105 1141 1165.7667 1188 1161.4212 1170.1121 1158.25 1165.0 1174.50
#> LZ1103 1073 1131.6667 1199 1120.0187 1143.3146 1109.00 1136.0 1154.00
#> LZ1100 1100 1151.2667 1214 1139.2032 1163.3302 1125.75 1148.5 1178.75
#> LZ1099 1078 1090.0333 1100 1087.9041 1092.1626 1085.00 1091.0 1094.00
#> LZ1097 1028 1112.2667 1212 1092.4442 1132.0891 1073.00 1119.0 1156.00
#> LZ1096  738  842.7667  996  818.1778  867.3556  789.00  841.0  893.00

## Jackknife resampling
jack <- jackknife(mc_dates)
head(jack)
#>             mean        bias      error
#> LZ1105 1162.0556   0.9444444  27.537909
#> LZ1103 1137.5556  -7.5555556  68.762698
#> LZ1100 1153.6111  -6.6111111  50.237614
#> LZ1099 1091.0556   0.9444444   9.860289
#> LZ1097 1091.6111  -6.6111111  70.898489
#> LZ1096  849.6667 147.3333333 268.508845