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eemUtils

The eemUtils package is a collection of useful functions that act as an expansion of the existing existing R fluorescence analysis framework provided by the eemR, staRdom and EEM packages. Many of the functions within this package are alterations or wrappers for existing functions from eemR, staRdom or EEM - thus, if you use the functions from this package, please allocate proper credit to those packages and their authors.

This package is a work in progress, and is subject to change. Always back up your data!

If you have any questions or comments, I can be reached at m.r.p.harris@keele.ac.uk.

Example functions

Below are some examples of functions within this package.

ggeem2

An updated EEM plotter, directly adapted from staRdom::ggeem(). It retains much of the same functionality, with tweaked graphical elements. Designed for use in my thesis and future pubs. It has integrated options for binning, and the default colour scheme takes after MATLAB’s ‘jet’ scheme. Below are two examples, using some Black Tea OM SRM.

pacman::p_load(eemUtils,staRdom,eemR,ggplot2,cowplot,pracma,magrittr,magick,tidyverse)
ILSMBT_36_eem_average <- (function(...)get(data(...,envir = new.env())))("ILSMBT_36_eem_average")
intp_eem <- eemUtils::interpolate_eem(ILSMBT_36_eem_average, n_pp = 2, verbose = FALSE)
p1 <- eemUtils::ggeem2(ILSMBT_36_eem_average, contour = TRUE, legend = FALSE, title_text = "Black tea 36-EEM avg") + theme(aspect.ratio = 1/1)
p2 <- eemUtils::ggeem2(intp_eem, bin_vals = "colpal", contour = FALSE, legend = FALSE, title_text = "Black tea 36-EEM avg interp + bin") + theme(aspect.ratio = 1/1)
cowplot::plot_grid(p1,p2,
                   ncol = 2, nrow = 1)

plot_eem_3D

A simple conversion of staRdom::eempf_comps3D(), but for use with sample EEM data, rather than outputs from a PARAFAC model. Extremely useful when checking individual samples for the presence of scatter lines or artefacts, or for quickly identifying the point of maximum fluorescence within part of an EEM. Option for the darker, MATLAB ‘jet’-esque colourscheme, or for a more vibrant rainbow as is used in staRdom.

To view a 3D, interactive render of the black tea from the two plots above, download the BlackTea_plot_eem_3D_widget html file in the ‘extras’ folder and open it with a suitable program (e.g. Chrome).

Generate_CORCONDIA

Generate_CORCONDIA() is a simple function wrapper for staRdom’s existing core consistency diagnostic function staRdom::eempf_corcondia(). It produces a more legible output.

extrpf_loadings

Use extrpf_loadings() to get the modeled per-sample fluorescence intensity loadings for each component within a set of PARAFAC models. This is a simple way to get quick series data from any number of PARAFAC models generated by staRdom::eem_parafac().

get_pfload_percent

Outputs from extrpf_loadings() can be immediately passed to get_pfload_percent(), which will calculate the percentage contribution of each modeled component to a given sample’s total fluorescence intensity.

extract_ramanpeak_areas

This function incorporates two methods in order to find the area under the Raman peak of water, for EEM data Raman normalisation purposes. The first method utilises a port of the MATLAB package drEEM’s RamanIntegrationRange function, which uses adjustable gradient detection to identify the start and end of the Raman peak. The method is presented and discussed at length in Murphy, 2011. The second method is a straightforward, fixed-range integration used by the Aqualog fluorometer, which assumes the Raman peak extends from 380nm to 410nm at 350nm excitation.

Some sample Raman curve spectra are included in the package as below.

library(pacman)
#> Warning: package 'pacman' was built under R version 4.0.5
pacman::p_load(eemUtils,ggplot2,cowplot,pracma,magrittr,magick)
data(SampleRamanCurves)
head(SampleRamanCurves)
#>   Wavelength Spectra.1 Spectra.2 Spectra.3 Spectra.4 Spectra.5
#> 1    246.355   0.19417   1.20432  -2.23798  -6.22403  -0.47937
#> 2    247.477  -5.24265  -0.40144  -1.22071  -1.19693   0.23968
#> 3    248.599  -1.94172  -1.00360   3.86560  -0.95754   0.95873
#> 4    249.721   5.24265   1.00360  -0.61036   4.30894   4.07461
#> 5    250.844   3.29229  -4.31084  -1.83981  -7.30603   2.16744
#> 6    251.966   3.02511   8.04115  -1.35844 -10.92216  -4.00087

extract_ramanpeak_areas() can then be used to get the areas under the raman peaks, and exported as image and/or .gif files for visualisation. The below .gif shows a use of the drEEM RamanIntegrationRange method, using gradient detection.

eemUtils::extract_ramanpeak_areas(RAMdat = SampleRamanCurves, range_upper = 500, method = "RIR", output_dir = NULL, gif = FALSE)
#> Legacy peak max at em397, lying between ex370:428
#> Registered S3 method overwritten by 'quantmod':
#>   method            from
#>   as.zoo.data.frame zoo
#> [01] IR = 381:409 | Peak Area = 2000.84287218425
#> [02] IR = 381:409 | Peak Area = 2005.96666376586
#> [03] IR = 381:408 | Peak Area = 1995.67397722841
#> [04] IR = 380:410 | Peak Area = 2041.30312091936
#> [05] IR = 378:408 | Peak Area = 2041.94451089284

This function can also optionally produce images or a .gif of the detected peak bounds and areas.

Installation

To get access to the functions in eemUtils, simply use the devtools package to install the package from github.

devtools::install_github("MRPHarris/eemUtils")

Update Notes

23/09/21 | An updated ggplot2-compatible EEM plotter, ggeem2(), has been added. This function updates the plotting provided by staRdom’s ggeem() function, tweaking the graphical parameters and adding an option for intensity value binning via eem_bin(). The check_eem() function has been removed, as it is no longer useful.

01/10/21 | ggeem2() now has multi-plot support, and inherits staRdom::ggeem()’s class handling.

17/01/22 | Various bug fixes. Gradually removing extrpf_spectra_or_eems(), as that workflow and associated functions have already been superseded by other functions in this package.

18/01/22 | Removed extrpf_spectra_or_eems(). Functionality provided by the functions extrpf_peak_spectra() and extrpf_eems(), which are easier to use and have more efficient syntax.

References

Massicotte, P. (2019). eemR: Tools for Pre-Processing Emission-Excitation-Matrix (EEM) Fluorescence Data. R package version 1.0.1. https://CRAN.R-project.org/package=eemR

Murphy, K. R. (2011). A Note on Determining the Extent of the Water Raman Peak in Fluorescence Spectroscopy. Applied Spectroscopy, 65(2), 233–236. https://doi.org/10.1366/10-06136

Murphy, K. R., Stedmon, C. A., Graeber, D., & Bro, R. (2013). Fluorescence spectroscopy and multi-way techniques. PARAFAC. Analytical Methods, 5, 6557–6566. doi: 10.1039/C3AY41160E

Pucher, M., Wünsch, U., Weigelhofer, G., Murphy, K., Hein, T., & Graeber, D. (2019). staRdom: Versatile Software for Analyzing Spectroscopic Data of Dissolved Organic Matter in R. Water, 11, 2366. doi: 10.3390/w11112366

Trivittayasil, V. (2016). EEM: Read and Preprocess Fluorescence Excitation-Emission Matrix (EEM) Data. R package version 1.1.1. https://CRAN.R-project.org/package=EEM