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Conversion between wt% and at%

Source: R/ASTR_conversion_atomic.R
atomic_conversion.Rd

Convert chemical compositions between weight percent (wt%) and atomic percent (at%). Results are always normalised to 100%.

Usage

wt_to_at(df, elements = colnames(get_unit_columns(df, "wtP")), drop = TRUE)

at_to_wt(df, elements = colnames(get_unit_columns(df, "atP")), drop = TRUE)

Arguments

df

Data frame with compositional data.

elements

Character vector with the chemical symbols of the elements that should be converted. Default are all columns in an ASTR object in the unit to be converted. See Details for further information

drop

If TRUE, the default, columns with unconverted values are dropped. If false, columns with unconverted values are kept and a suffix added to the column names of the converted values.

  • _atP for conversions to atomic percent

  • _wtP for conversions to weight percent.

Value

The original data frame with the converted concentrations normalised to 100%.

Details

The column names of the elements to be converted must be equivalent to their chemical symbols. The functions convert only values in wt% or at%. If concentrations are present in another concentration unit (e.g. ppm, µg/kg), run unify_concentration_unit(df, "wtP") first to convert all concentrations to wt%. If df is an ASTR object, only elements will be converted to at%, and oxides in wt% are automatically excluded. To convert oxides into at% and vice versa, convert to wt% first.

Examples


library(magrittr)

# Convert weight percent to atomic percent and to weight percent
df <- data.frame(ID = 1, Si = 46.74, O = 53.26)  # SiO2 composition
at <- wt_to_at(df, elements = c("Si", "O"))
at_to_wt(at, elements = c("Si", "O"))
#>   ID    Si     O
#> 1  1 46.74 53.26

# preserve columns with unconverted values
wt_to_at(df, elements = c("Si", "O"), drop = FALSE)
#>   ID    Si     O   Si_atP    O_atP
#> 1  1 46.74 53.26 33.32926 66.67074

# Use with ASTR objects
# Create ASTR object
test_file <- system.file("extdata", "test_data_input_good.csv", package = "ASTR")
arch <- read_ASTR(test_file, id_column = "Sample", context = 1:7)
#> Warning: 39 missing values across 12 analytical columns
#> Warning: See the full list of validation output with: ASTR::validate(<your ASTR object>).

# Convert columns in wt% to at%
arch_atP <- wt_to_at(arch)

# To convert all applicable concentrations, unify units first:
arch_all <- unify_concentration_unit(arch, "wtP") %>%
  wt_to_at()

# Elements already present in the converted unit are ignored.
rowSums(get_unit_columns(arch_all, "atP")[-1], na.rm = TRUE) > 100
#>  [1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE
#> [13]  TRUE  TRUE