Emscorr
Purpose
Extended multiplicative scatter correction (EMSC) preprocessing.
Synopsis
- [sx,fx,xref,reg,res] = emscorr(x,xref,options)
Description
EMSCORR attempts to remove additive and multiplicative scattering effects in spectra. This can be thought of as a filter where some portions of the signal are passed and some are rejected. The input (x) is a MxN matrix (class "double") of M spectra measured at N channels. Each row of (x) is regressed against input (xref) and the results are used to 'correct' (x). If (xref) is not input then mean(x) is used.
There are several options to allow for weighted least squares (i.e. to de-weight channels that should not be included in the regression), including different spectra that should be filtered out, and including spectra that should not be filtered out.
The outputs are (sx) the corrected spectra, (fx) the signal that was filtered out, and (xref) the reference spectrum. Outputs (reg) are the regression coefficients and (res) is a MxN matrix of residuals. For non-windowed filtering, (reg) is [number of coefficients] x M. The number of coefficients corresponds to the number of basis vectors included in the correction. The coefficients are ordered according to the following basis: xbase = [xref, 1 x x2 ..., options.p, options.s]. If a windowed filter is used, (reg) is [number of coefficients] x N x M. where mode 2 corresponds to the windows.
Inputs
- first = first input is this.
Optional Inputs
- second = optional second input is this.
Outputs
- firstout = first output is this.
Options
options = a structure array with the following fields:
- plots: [ {'none'} | 'final' ] governs plotting of results, and
- order: positive integer for polynomial order {default = 1}.
Example
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