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Quick guide to PLS

Quick guide to PLS. Use [Alt-Tab] to go to LatentiX (if running) Press [Page Down] or [Enter] to continue Press [ESC] to end the show. Dioxin and fatty acid data.

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Quick guide to PLS

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  1. Quick guide to PLS Use [Alt-Tab] to go to LatentiX (if running) Press [Page Down] or [Enter] to continue Press [ESC] to end the show

  2. Dioxin and fatty acid data • ProblemTo develop a PLS model that can predict the dioxin concentration (y) in ng/(kg fat) in fish meal samples from fatty acids profiles (X).In total 64 samples were analysed and gas chromatography was used for the determination of 32 fatty acids (including an unidentified group). The results are given in % of all 32 fatty acids.The very expensive and complex dioxin analyses were performed by a German laboratory. • DataThe dimension of the data structure is 64 objects x 34 variables.The first two variables are the species code (herring, sprat, blue whiting, sand eel etc. in total 15 species) and the dioxin content.Variables 3 to 34 are the chromatographic variables.Source: Rapid dioxin assessment in fish products by fatty acid pattern recognition, Marc Bassompierre, Lars Munck, Rasmus Bro and Søren Balling Engelsen, Analyst, 129, 553-558, 2004.

  3. Get the data

  4. The data in the WorkBench

  5. Select the fatty acid variables Write 3:34 and press [ENTER] or select the fatty acid variables in the Variables listbox

  6. Define a variable set

  7. Give the set a name, e.g. X

  8. Now select dioxin in the listbox The plot window always show the actual selection in the Objects and Variables listboxes

  9. Plot dioxin as a function of the objects Click on this icon

  10. Define a variable set containing only the dioxin variable

  11. Give the set a name, e.g. y

  12. Autoscale the X data Then select autoscale First select X in the Sets box

  13. The effect is shown instantly in the plot Click Transform to see how the transformation affects the data

  14. Make a PLS model Select PLS in the dropdown menu

  15. Select the dependent variable(s) Then select y (or click on Dioxin in the listbox) First select y in the Sets box

  16. Autoscale y

  17. Choose cross validation Select CV: Syst123 (Venetian blinds)

  18. Choose the number of segments In this case we use eight segments

  19. Calculate the PLS model Then press OK Press Calculate

  20. Plot the error

  21. RMSEC & RMSECV Select both using CTRL

  22. U vs T plot

  23. U vs T plot TIP: use the arrows keys to change the number of components Change the markers & labels

  24. Plot regression coefficicents

  25. Regression coefficients TIP: use the arrows keys to change the number of components Change the markers & labels

  26. Plot Actual vs Predicted

  27. Actual vs Predicted for six components TIP: use the arrows keys to change the number of components Change the markers & labels THE END

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