Coda dw
Purpose
Variable selection method for hyphenated methods with a mass spectropmeter as a detector. The variables (mass chromatograms) are selected on the basis of smoothness.
Synopsis
- [dw_value,dw_index] = coda_dw(data,level);
Description
CODA_DW the Durbin Watson values of the first derivative of the chromatograms in data. The optional argument level defines the limitit of Durbin Watson value used for a plot of the results. If level is an integer it is used to plot the best level chromatograms. Low values for Durbin Watson indicate good quality chromatograms. The Durbin Watson values (dw_values) as wel as their ranking indices (dw_index) (low to high, so good to low quality) . For more information the Durbin Watson method see the function DURBIN_WATSON. Input data can be a matrix with the data or a datasetobject
Examples
Plotting the chromatograms with a Durbin Watson value less than 2.2.
coda_dw(data,2.2);
Plotting the best 40 chromatograms.
coda_dw(data,40);
Algorithm
The algorithm calculates the Durbin Watson values of the first derivative of the mass chromatograms.