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Calculate the fluorescence humification index (HIX)

Source: R/eem_metrics.R
eem_humification_index.Rd

The fluorescence humification index (HIX), which compares two broad aromatic dominated fluorescence maxima, is calculated at 254 nm excitation by dividing the sum of fluorescence intensities between emission 435 to 480 nm by the the sum of fluorescence intensities between 300 to 345 nm.

Usage

eem_humification_index(eem, scale = FALSE, verbose = TRUE)

Arguments

eem

An object of class eemlist.

scale

Logical indicating if HIX should be scaled, default is FALSE. See details for more information.

verbose

Logical determining if additional messages should be printed.

Value

An object of class eemlist.

A data frame containing the humification index (HIX) for each eem.

Interpolation

Different excitation and emission wavelengths are often used to measure EEMs. Hence, it is possible to have mismatchs between measured wavelengths and wavelengths used to calculate specific metrics. In these circumstances, EEMs are interpolated using the interp2 function from the parcma library. A message warning the user will be prompted if data interpolation is performed.

References

Ohno, T. (2002). Fluorescence Inner-Filtering Correction for Determining the Humification Index of Dissolved Organic Matter. Environmental Science & Technology, 36(4), 742-746.

doi:10.1021/es0155276

See also

interp2

Examples

file <- system.file("extdata/cary/scans_day_1/", package = "eemR")
eem <- eem_read(file, import_function = "cary")

eem_humification_index(eem)
#> Warning: This metric uses either excitation or emission wavelengths that were not present in the data. Data has been interpolated to fit the requested wavelengths.
#> Warning: This metric uses either excitation or emission wavelengths that were not present in the data. Data has been interpolated to fit the requested wavelengths.
#> Warning: This metric uses either excitation or emission wavelengths that were not present in the data. Data has been interpolated to fit the requested wavelengths.
#> Warning: This metric uses either excitation or emission wavelengths that were not present in the data. Data has been interpolated to fit the requested wavelengths.
#>    sample        hix
#> 1    nano  0.5568136
#> 2 sample1  6.3795618
#> 3 sample2  4.2548483
#> 4 sample3 13.0246234