25 oct. 2013

Applying "SNV + Detrend" to the spectra with R

Normally Detrend is used together with SNV as a Math treatment to remove the scatter. We have seen in the last post, how to apply Detrend to the spectra using the R package "pracma".
There are other posts in this blog about SNV (standard normal variate), and we can combine them to get the SNV + Detrend math treatment.
First let´s apply the SNV:
wavelengths1<-seq(1,268,by=1)  #para "yarn"
matplot(wavelengths1,yarn_snv,type="l",main="Yarn spectra with +SNV",xlab="Wavelength (nm)",ylab="1/R (log 1/R)",lty=1,col=1)


and now the Detrend:




23 oct. 2013

Applying "Detrend" to the spectra with R

There is a nice math treatment I use to apply to the spectra in NIR. It is the Detrend.
Normally goes together with the SNV, but this time I´m going to apply it alone.
I´m going to use the Yarn data, with this raw spectra:

Now we load the R package "pracma":
wavelengths1<-seq(1,268,by=1)  #para "yarn"
The spectra change to this one:
We can see hou the "trend" effect ( a shift in the baseline) is corrected and the baseline adjusted.