Copper classification according to Bray et al. (2015)

Classification of copper artefacts according to Bray et al. (2015) into one of 16 trace element compositional groups based on As, Sb, Ag, or Ni being below or above 0.1 wt%.

Usage

copper_group_bray(
  df,
  elements = c(As = "As", Sb = "Sb", Ag = "Ag", Ni = "Ni"),
  id_column = "ID",
  group_as_number = FALSE,
  ...
)

Arguments

df

data frame with the data to be classified.

elements

named character vector with the column names of the As, Sb, Ag, and Ni concentrations.

id_column

name of the column in df with the identifiers of each row. Default to ID.

group_as_number

logical. If FALSE, the default, copper groups are reported as their label. Otherwise, copper groups are reported by their number.

...

Additional arguments for unit conversion, see atomic_conversion and oxide_conversion for details.

Value

If df is an ASTR object, the output is an object of the same type including the ID column, the contextual columns, the elements used for classification and the alloy type. In all other cases, the data frame provided as input with the column for the alloy type.

References

Bray, P., Cuénod, A., Gosden, C., Hommel, P., Liu, P. and Pollard, A. M. (2015), Form and flow: the ‘karmic cycle’ of copper. Journal of Archaeological Science 56, pp. 202-209. https://doi.org/10.1016/j.jas.2014.12.013.

See also

Other copper alloy classifications: copper_alloy_bb(), copper_alloy_pollard()

Examples

# create dataset
sample_df <- data.frame(
  ID = 1:3,
  As = c(0.2, 0.01, 0.15),
  Sb = c(0.00, 0.2, 0.11),
  Ag = c(0.00, 0.00, 0.12),
  Ni = c(0.00, 0.05, 0.20)
)
# classify copper groups
copper_group_bray(sample_df)
#>   ID   As   Sb   Ag   Ni copper_group_bray
#> 1  1 0.20 0.00 0.00 0.00                As
#> 2  2 0.01 0.20 0.00 0.05                Sb
#> 3  3 0.15 0.11 0.12 0.20       As+Sb+Ag+Ni

# classification with group number as output
copper_group_bray(sample_df, group_as_number = TRUE)
#>   ID   As   Sb   Ag   Ni copper_group_bray
#> 1  1 0.20 0.00 0.00 0.00                 2
#> 2  2 0.01 0.20 0.00 0.05                 3
#> 3  3 0.15 0.11 0.12 0.20                16

# For ASTR objects, units and oxides are automatically converted
sample_df2 <- as_ASTR(
  data.frame(
    ID = 1:3,
    As2O3_wtP = c(0.2, 0.01, 0.15),
    Sb2O3_wtP = c(0.00, 0.2, 0.11),
    Ag2O_wtP = c(0.00, 0.00, 0.12),
    NiO_wtP = c(0.00, 50, 0.20)
  )
)
copper_group_bray(sample_df2, elements = c(As = "As2O3", Sb = "Sb2O3", Ag = "Ag2O", Ni = "NiO"))
#> ASTR table
#> Analytical columns: As, Sb, Ag, Ni
#> Contextual columns: copper_group_bray 
#> # A data frame: 3 × 6
#>      ID      As     Sb    Ag     Ni copper_group_bray
#>   <int>   [wtP]  [wtP] [wtP]  [wtP] <chr>            
#> 1     1 0.151   0      0      0     As               
#> 2     2 0.00757 0.167  0     39.3   Sb+Ni            
#> 3     3 0.114   0.0919 0.112  0.157 As+Ag+Ni