Posts Tagged ‘ "R" Chemometrics ’

R^2 Spectrum

April 21, 2012
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R^2 Spectrum

We have seen in the previous post, how to calculate the correlation spectrum, but other simple way to show  how the bands correlate to the constituent of interest is to calculate R^2. This way we remove the negative part of the correlation spectru...

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"Correlation / Covariance" Spectrum (This time with "R")

April 18, 2012
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"Correlation / Covariance"  Spectrum (This time with "R")

I treat this matter with other software´s, and of course you can do the same with "R".Once I have the spectra of my samples with a math treatment, I want to draw a correlation spectrum to see which wavelengths have better correlation with the constitu...

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More Spectra patterns (1ª derivative)

April 17, 2012
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More Spectra patterns (1ª derivative)

In the case of the first derivative for the absortion band, the maximum becomes a cero crossing.Using SG filters, we can calculate it with R, and to see, like in the last posts, the Corrgram matrix.Corrgram for the first derivative for this band:L...

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Math Spectra Patterns

April 16, 2012
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Math Spectra Patterns

I was working today with "R" to get more patterns with the Corrgram. In the demo raw spectra I wanted this time to look to a band as much Gaussian as possible. I select it and trim the spectra to that region treated with the MSC ("Multiple Scatter Corr...

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CORRGRAM: Correlation Matrix (Wavelengths)

April 13, 2012
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CORRGRAM: Correlation Matrix (Wavelengths)

With the "Corrgram" package we can see patterns that can help us to recognize possible inter-correlations in a big matrix. This could be the case to see the correlation to every wavelength respect to all others. This way we can see the high correlation...

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CORRGRAM: Correlation Matrix (Constituents)

April 12, 2012
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CORRGRAM: Correlation Matrix (Constituents)

Thanks a lot to Kevin W., for his comment in my previous post.Corrgram, it a nice package and I found very nice information to understand it a little bit better on Internet apart from the R help page.Corrgrams: Exploratory displays for correlation matr...

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Correlation Matrix (Constituents)

April 9, 2012
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Correlation Matrix (Constituents)

It is important to understand as better as possible our sample set before to develop the regression. Continuing with the “Y” matrix (constituent’s matrix) we have to observe the correlation matrix.In the R Graph Gallery, we can get the code to dr...

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Looking to the difference spectrum

April 9, 2012
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Looking to the difference spectrum

From the previous post, we can make the difference spectrum (once the samples are sorted by moisture) between the sample with the lowest moisture value (position 1), from the sample with the highest moisture value (position 66). This spectra will help ...

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Sorting the "Sample Sets" by constituents

April 8, 2012
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Sorting the "Sample Sets" by constituents

I use to see the videos from:http://www.twotorials.com/and the video:How to order and sort stuff in Ris really useful to apply this concept to organize and understand better our sample sets before to proceed to develop a calibration.The idea of this po...

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VIDEO: "R" Checking the reference values ("Y" Matrix).

March 30, 2012
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VIDEO: "R" Checking the reference values ("Y" Matrix).

(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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