Reduces the number of channels of spectra by replacing each group of
width adjacent channels by their mean.
Arguments
- x
A numeric matrix or data frame of spectra, one per row, or a numeric vector (one spectrum). Their names are the wavelengths.
- width
The number of adjacent channels averaged, a positive integer. Default is 3;
width = 1returns the spectra unchanged.- segments
A logical: bin the segments between gaps of the wavelength axis separately (
TRUE, default). Needs wavelengths as names.
Value
The binned spectra, of the same type as x (a tibble for a data
frame), with ceiling(n / width) channels for each detector segment of
n channels.
Details
Averaging keeps the intensities on their scale and divides the noise of
independent channels by about sqrt(width), at the cost of spectral
resolution: keep width smaller than the width of the emission lines (a
few channels in LIBS spectra) to keep them resolved. Fewer channels also
make the models faster to fit.
The channels are grouped from the first one; when their number is not a
multiple of width, the last group is smaller. When segments = TRUE, the
spectrum is split between the detectors of a multi-spectrometer system
(where the wavelengths step back, or jump by more than 5 times the median
spacing), and each detector is binned on its own, so that no group
straddles two detectors. The binned channels are named by their mean
wavelength (to 10 significant digits), or, when the names are not
wavelengths, by the name of their first channel; a channel left alone in
its group keeps its name.
References
Vrábel, J., Képeš, E., Duponchel, L., et al. (2020). Classification of challenging laser-induced breakdown spectroscopy soil sample data - EMSLIBS contest. Spectrochimica Acta Part B, 169:105872.