Description Usage Arguments Details Value Author(s) References See Also Examples
View source: R/SolventSuppression.R
Signal smooting for water residuals resonance removal.
1 2  SolventSuppression(Fid_data, lambda.ss = 1e6, ptw.ss = TRUE,
returnSolvent = FALSE, verbose = FALSE)

Fid_data 
Matrix containing the FIDs, one row per signal, as outputted by 
lambda.ss 
Penalty on roughness used to calculate the smoothed version of the FID. The higher lambda is, the smoother the estimated solvent signal will be. 
ptw.ss 
If 
returnSolvent 
If 
verbose 
If 
FIDs usually present a wavy shape. Under the assumption that water is the main compound of the analyzed samples, its signal can be modelled by the smoothing of the FIDs. We then subtract this wave, i.e. the solvent residuals resonance signal, from the original FIDs.
The smoothing is done with a Whittaker smoother which is obtained by the minimization of
V + λ R
where
V is the sum of the squared differences between the original and the smoothed signal.
R measures the roughness of the estimated signal.
The larger λ is, the smoother the solvent residuals resonance signal. Eilers (2003) and Frasso & Eilers (2015) suggest different ways to tune λ in order to optimise the smoothing: either visually, by crossvalidation or using the Vcurve procedure.
If returnSolvent = TRUE
, will return a list with the following elements: Fid_data
, SolventRe
and SolventIm
. Otherwise, the function will just return Fid_data
.
Fid_data 
The matrix of FIDs with the solvent residuals signal removed. 
SolventRe 
The real part of the solvent signal. 
SolventIm 
The imaginary part of the solvent signal. 
Benoît Legat, Manon Martin & Paul H. C. Eilers
Martin, M., Legat, B., Leenders, J., Vanwinsberghe, J., Rousseau, R., Boulanger, B., & Govaerts, B. (2018). PepsNMR for 1H NMR metabolomic data preprocessing. Analytica chimica acta, 1019, 113.
Frasso, G., & Eilers, P.H.C. (2015). Land Vcurves for optimal smoothing. Statistical Modelling, 15(1), 91111.
Rousseau, R. (2011). Statistical contribution to the analysis of metabonomics data in 1H NMR spectroscopy. PhD thesis. Institut de statistique, biostatistique et sciences actuarielles, Université catholique de Louvain, Belgium.
Eilers, P.H.C. (2003). A perfect smoother. Analytical Chemistry, 75(14), 36313636.
See also BaselineCorrection
which also uses the Whittaker smoother.
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