Mscorr: Difference between revisions
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===Purpose=== | ===Purpose=== | ||
Multiplicative scatter/signal correction (MSC). | Multiplicative scatter/signal correction (MSC). | ||
===Synopsis=== | ===Synopsis=== | ||
:[sx,alpha,beta,xref] = mscorr(x,xref,mc,win,specmode,subind) | :[sx,alpha,beta,xref] = mscorr(x,xref,mc,win,specmode,subind) | ||
===Description=== | ===Description=== | ||
MSCORR performs multiplicative scatter correction (a.k.a. multiplicative signal correction) on an input matrix of spectra x (class "double") regressed against a reference spectra xref (class "double"). If (xref) is empty or omitted, the mean of (x) is used as the reference. | MSCORR performs multiplicative scatter correction (a.k.a. multiplicative signal correction) on an input matrix of spectra x (class "double") regressed against a reference spectra xref (class "double"). If (xref) is empty or omitted, the mean of (x) is used as the reference. | ||
If the optional input ''mc'' is 1 {default} then an intercept is used. If ''mc'' is set to 0 (zero) then a force fit through zero is used. | If the optional input ''mc'' is 1 {default} then an intercept is used. If ''mc'' is set to 0 (zero) then a force fit through zero is used. | ||
Optional input ''win'' is a ''NK'' element cell array of indices corresponding to windows to perform MSC, i.e. MSC is performed in each window win{i} for ''i=1:NK''. In this case, (alpha and beta are not assigned). Optional input (specmode) defines which mode of the data is the spectral mode (default = 2) and is only used when (x) contains 3 or more modes. Optional input (subind) specifies the indices within the included spectral variables that are used to calculate the MSC correction factors (alpha and beta); default is that ALL included spectral variables are used. | Optional input ''win'' is a ''NK'' element cell array of indices corresponding to windows to perform MSC, i.e. MSC is performed in each window win{i} for ''i=1:NK''. In this case, (alpha and beta are not assigned). Optional input (specmode) defines which mode of the data is the spectral mode (default = 2) and is only used when (x) contains 3 or more modes. Optional input (subind) specifies the indices within the included spectral variables that are used to calculate the MSC correction factors (alpha and beta); default is that ALL included spectral variables are used. | ||
Outputs are the corrected spectra sx, the intercepts/offsets alpha, the multiplicative scatter factor/slope beta, and the reference spectrum xref. | Outputs are the corrected spectra sx, the intercepts/offsets alpha, the multiplicative scatter factor/slope beta, and the reference spectrum xref. | ||
===Algorithm=== | ===Algorithm=== | ||
For input spectra '''x''' (1x''N'') and reference spectra '''x'''<sub>ref</sub> (1x''N'') the model is: | For input spectra '''x''' (1x''N'') and reference spectra '''x'''<sub>ref</sub> (1x''N'') the model is: | ||
'''x'''<sup>T</sup>? + ? = '''x'''<sup>T</sup><sub>ref</sub> . | '''x'''<sup>T</sup>? + ? = '''x'''<sup>T</sup><sub>ref</sub> . | ||
and the corrected spectra '''x'''<sub>s</sub> (1x''N'') is given by: | and the corrected spectra '''x'''<sub>s</sub> (1x''N'') is given by: | ||
'''x'''<sub>s</sub> = ('''x'''<sub>ref</sub> -?)/? . | '''x'''<sub>s</sub> = ('''x'''<sub>ref</sub> -?)/? . | ||
===See Also=== | ===See Also=== | ||
[[frpcr]], [[stdfir]], [[stdgen]] | [[frpcr]], [[stdfir]], [[stdgen]] | ||
Revision as of 15:25, 3 September 2008
Purpose
Multiplicative scatter/signal correction (MSC).
Synopsis
- [sx,alpha,beta,xref] = mscorr(x,xref,mc,win,specmode,subind)
Description
MSCORR performs multiplicative scatter correction (a.k.a. multiplicative signal correction) on an input matrix of spectra x (class "double") regressed against a reference spectra xref (class "double"). If (xref) is empty or omitted, the mean of (x) is used as the reference.
If the optional input mc is 1 {default} then an intercept is used. If mc is set to 0 (zero) then a force fit through zero is used.
Optional input win is a NK element cell array of indices corresponding to windows to perform MSC, i.e. MSC is performed in each window win{i} for i=1:NK. In this case, (alpha and beta are not assigned). Optional input (specmode) defines which mode of the data is the spectral mode (default = 2) and is only used when (x) contains 3 or more modes. Optional input (subind) specifies the indices within the included spectral variables that are used to calculate the MSC correction factors (alpha and beta); default is that ALL included spectral variables are used.
Outputs are the corrected spectra sx, the intercepts/offsets alpha, the multiplicative scatter factor/slope beta, and the reference spectrum xref.
Algorithm
For input spectra x (1xN) and reference spectra xref (1xN) the model is:
xT? + ? = xTref .
and the corrected spectra xs (1xN) is given by:
xs = (xref -?)/? .