In all the textbooks related to chemometrics, PLS has been described as a regression technique that requires a dependent and independent variable for generating a regression line. However, in some chemometric softwares (especially Unscrambler), the while using PLS it shows an score plot (similar to PCA). It seems they are using PLS-DA. I am unable to understand what they are doing as no regression line has been generated.
The following figure corresponds to a study on liquor samples from three different geographical regions. We have applied PLS (it seems it is PLS-DA, not PLSR) in unscrambler. It has classified samples. However, I am unable to understand how to interpret it and whether it is accurate or not.
PLS-DA is a supervised pattern recognition technique, used to classify the unknown samples to the predefined class.
In this technique, each sample in the calibration set is assigned a dummy variable as a reference value (you need to add new column and assign each sample to its class), which is an arbitrary number designating whether the sample belongs to a particular group or not for example (1 = Class A and 2 = Class B). A sample is classified as A if its value was below 1.5 and classified as B if the value was above 1.5.
The following paper applied the PLS-DA technique for classifying honey based its botanical origin.Article Characterization and Discrimination of the Floral Origin of ...
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