Articles by jrcuesta

Olive Oil NIR/VIS Spectra – 001 (ChemSpec)

June 25, 2012 | jrcuesta

I continue with the practicing with ChemSpec, and this time I import seven spectra of olive oil. This time I have been more careful and I have the frequency column as numeric form the CSV file. Once I have the spectra (with and offset):Take in account ...
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My first "ChemoSpec" spectra

June 21, 2012 | jrcuesta

I’ve been this week trying to import some spectra to ChemoSpec (R Package), at the beginning I had problems generating the “csv”  files, and the function getManyCsv did not recognize the files. I did not have properly configured the regional...
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Should I adjust the slope?

June 11, 2012 | jrcuesta

I add a new video “Should I adjust the slope”, where a new part of script is added to the monitor function.  I don´t recommend adjusting the slope, but there are circumstances where it is necessary:Suppose you have an equation, but not the ca...
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F-test to find UECLs

June 5, 2012 | jrcuesta

I have fixed the link to the video "Removing Y outliers from the validation set" and it´s time to see what could be the next step to the function. As we know the RMSEP is the sum of the explained (BIAS) and unexplained error (SEP). We get also the ...
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Exporting from Win ISI / Importing into R

May 29, 2012 | jrcuesta

Chemometric software´s  have the option to export a matrix to a TXT file (in this case a constituents matrix), in a way we can import it easily into R, to work with. It is the first step to go into the R world.I use in this case Win ...
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Monitor: Adding "RER" and "RPD" statistics

May 25, 2012 | jrcuesta

I continue developing the Monitor function in R. The idea is to get statistics which help me to understand the performance of my model.Of course the validation set must be free of outliers (X or Y).I add this time two new statistics: RER and ...
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Improving script_002: “Monitor”

May 15, 2012 | jrcuesta

I read in an article that Ian Cowe said that what normally chemometricians do is to look to the graphics, of course interpret those graphics. So I still go on trying to develop a function can help me to understand the graphics and all the statistics th...
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Should I adjust the Bias?

May 10, 2012 | jrcuesta

A bias or systematic error is quite common when monitoring predictions vs reference data. Anyway we must have certain control limits to decide if the Bias is significant or not. Procedures (as for example ISO 12099 )give details about how to calculate ...
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Improving script_001: “Monitor”

May 6, 2012 | jrcuesta

After having a look to this video: from rtwotutorials, and reading some tutorials, I decided to modified the script from the previous post: Practicing Script with “ R”: Monitor , in order to make it more r...
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Practicing Script with “ R”: Monitor

May 4, 2012 | jrcuesta

These are  samples analyzed by a reference method (column: Protein) and by an analytical method with a certain model (column: IFTpro). The idea is to create a Monitor Report for some basic statistics (RMSEP, Bias, SEP, R,RSQ) to see how ...
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Monitoring some statistics with "R"

May 1, 2012 | jrcuesta

I´ve been practicing after reading a couple of tutorials:R: A self-learn tutorialProgramming in Rto create a basic function  to monitor some  basic statistics as RMSEP, Bias, SEP, Correlation and RSQ. I´ve been doing this with other so...
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R^2 Spectrum

April 21, 2012 | jrcuesta

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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More Spectra patterns (1ª derivative)

April 17, 2012 | jrcuesta

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 | jrcuesta

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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