Posts Tagged ‘ "R" Chemometrics ’

Comparing Spectra with different math treatments

March 30, 2012
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Comparing Spectra with different math treatments

It is amazing the quantity of graphics you can develop with R, and how you can show and manage  these graphics. Here in the same plot we compare the raw demo spectra, treated with MSC, SNV and with the first derivative (differences between consecu...

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Dividing the Sample Set in two (Validation & Training)

March 29, 2012
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Dividing the Sample Set in two (Validation & Training)

We have in the Demo sample set “66” samples.  In this post we´ll see one way to divide the set in two parts: one for “Validation” and another for Training or Calibration.The selection will be random. And we are going to use the command:

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SCRIPT for NIR "DEMO" Tutorial – 001

March 28, 2012
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SCRIPT for NIR "DEMO" Tutorial – 001

########### RAW NIR Demo Data##################################demo<-read.table("demo.txt",header=TRUE)VIS<-demoVIS<-as.matrix(VIS)NIR<-demoNIR<-as.matrix(NIR)ALL<-demoALL<-as.matrix(ALL)Protein<-demo...

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VIDEO: Applying "SNV" math-treatment to our raw spectra in "R".

March 26, 2012
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VIDEO: Applying "SNV" math-treatment to our raw spectra in "R".

(This article was first published on NIR-Quimiometría, and kindly contributed to R-bloggers) To leave a comment for the author, please follow the link and comment on his blog: NIR-Quimiometría. R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics...

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VIDEO: Applying "MSC" math-treatment to our raw spectra in "R".

March 25, 2012
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VIDEO: Applying "MSC" math-treatment to our raw spectra in "R".

(This article was first published on NIR-Quimiometría, and kindly contributed to R-bloggers) To leave a comment for the author, please follow the link and comment on his blog: NIR-Quimiometría. R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics...

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VIDEO:Looking to "NIR" Spectra in "R": (Import and organize)

March 24, 2012
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VIDEO:Looking to "NIR" Spectra in "R":  (Import and organize)

 

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Applying Savitzky-Golay filters in “R”

March 20, 2012
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Applying Savitzky-Golay filters in “R”

(This article was first published on NIR-Quimiometría, and kindly contributed to R-bloggers) When applying SG, we select a moving average window with an odd value “n” for the number of data points. SG fit a polynomial of “p” degree to this data points and give the value to the central point (this is the reason to have an odd...

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Savitzky-Golay filters in R

March 17, 2012
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Savitzky-Golay filters in R

Derivatives are a good way to extract information to our spectra. As we know NIR contents overlapping bands, and spectra must be treated with math operations in order to extract as much information as possible and to correlate it with the constituent &...

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NIT: Fatty acids study in R – Part 007

March 14, 2012
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NIT: Fatty acids study in R – Part 007

Once we have chosen the model, we can continue acquiring spectra of new samples. Spectra is exported to a txt or csv file and we imported in R to be reprocessed.We use the function “predict” from the PLS package. I have done this with 20 new sample...

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NIT: Fatty acids study in R – Part 006

March 12, 2012
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NIT: Fatty acids study in R – Part 006

In one of the columns, for constituent C16_0, one sample (57) has a value of “zero” (we could see this in the histogram).The reason for that is that the laboratory did not supply this value. The PLS regression will consider the lab value as cero, s...

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