12 mar. 2019

Over-plotting validation and training data in the Mahalanobis ellipses

One of the great things of R is that we can get the code of the different functions (in this case the function "drawMahal" from the package "Chemometrics" ) and adapt this code to our necessities.
I wanted to over-plot the training set scores for the first and second principal components with the scores of the validation set, which are redundant samples taken apart in a selection process with the function "puchwain" from the package "prospectr", but I get problems with the scale due to the way "drawMahal" fix the X and Y limits. But editing the function we can create a personalize function for our case and to compare the redundant samples in red with the training samples in black.
Now the next is to over-plot the test samples (in theory bad samples) in another color in a coming post.

24 feb. 2019

Scatter Correction Spectra plots with R

These are the spectra of an Infratec 1241 for Soy meal treated with "Multiple Scatter Correction", "Standard Normal Variate" and "Standard Normal Variate  + Detrend", apart from the "Raw Spectra".

All this math treatments are in the new Video Series (in spanish) from the posts last weeks.

In next post we see the effect of derivatives in the spectra, and we continue with Principal Components and Regressions Methods.