Plotting the “Mean Spectrum”

Mean spectrum calculation is important:

To center a matrix of spectra, we subtract the mean spectrum, from every spectrum in the matrix.

There are also many options to use the mean spectrum, like average subsamples.

Let´s calculate and plot the mean spectra for the Yarn NIR Data:

> yarn_mean<-colMeans(yarn$NIR)

> wavelength<-c(1:268)

> matplot(wavelength,yarn_mean,lty=1,pch=21,col="red",

  + xlab="data_points",ylab="mean spec.")

We can see in the following plot the X matrix centered:

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