# Posts Tagged ‘ "R" Chemometrics ’

## "R": Plotting the spectra (Gasoline) – 002

February 2, 2012
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"R" has a package called "ChemometricsWithR", where we can get data from different analytical instruments including Near Infrared (NIR).Follow the steps to plot the spectra of a gasoline data set:In this other case we plot the spectra of the NIR shootout 2002: > data(shootout)> wavelengths<-seq(600, 1898,by=2)> mattplot(wavelengths,shootout\$calibrate.1,xlab="wavelength(nm)",ylab="log1/R)")>...

## "R": Looking at the Data (Gasoline) – 001

February 1, 2012
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As other softwares "R" has nice tools to look to the data before to develop the calibration.Statistics for the "Y" variable (in this case octane number) like Maximun, Minimun,..,standard deviation,...are important:> library(ChemometricsWithR)> data(gasoline)> summary(gasoline\$octane)   Min.  1st Qu.  Median    Mean   3rd Qu.    Max.   83.40   85.88    87.75    87.18   88.45    89.60> sd(gasoline\$octane) 1.530078And of course the Histogram:> hist(gasoline\$octane)

## NIPALS: Principal Components Analysis with "R" (Part: 002)

January 1, 2012
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We started some posts based on the tutorials of:"Multivariate Statistical Analysis using the R package chemometrics"The first post was:Principal Components Analysis with "R" (Part: 001)Now we continue with a second part.The graphics help us to dec...

## IRIS Flower Data Set (R-003)

December 19, 2011
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Centramos la matriz con el comando, generando a partir de A una nueva matriz que llamamos "Acentered"Acentered=scale(A,center=T)Ahora con la función "eigen":Esta es otra forma de proceder con el cálculo de los componentes principales (eigenvectors y ...

## IRIS Flower Data Set (R-002)

December 17, 2011
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Ver  primero: IRIS Flower Data Set (R-001)See first:        IRIS Flower Data Set (R-001)El comando "summary" nos ayuda a comprender la importancia de cada componente principal:Los "eigenvalues" son las desviacion...

## IRIS Flower Data Set (R-001)

December 17, 2011
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IRIS Flower Data SetEste es el Link a Wikipedia donde podéis encontrar los datos que utilizó Fisher en su trabajo de 1936. Ya hemos trabajado con estos datos en Excel y los continuaremos usando en nuevas entradas.En este link, podemos ver las fotos de las flores (IRIS en castellano son lírios).Represento como LS (longitud del sépalo), AS...

December 12, 2011
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Ver primero: PCA file calculation with "R"See first:         PCA file calculation with "R"Podemos ver los diferentes planos que forman los PCs entre sí, con la función "Pairs" de "R".We can see all the combinat...

## Principal Components Analysis with "R" (Part: 001)

December 7, 2011
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This is the first "post" of my new adventure with a software that I consider very interesting and that give to people the oportunity to work with Chemometrics ("R" is free).To follow these examples, yo can download the following article:"Multivariate S...

## PCA file calculation with "R".

December 5, 2011
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X es la matriz centrada (X is the centered matrix). Xcov es la matriz de covarianzas de X (Xcov is the covariance matrix of X).Con la función "eigen" calculamos los "eigenvectors" y "eigenvalues" de Xcov.(With the function "eigen" we calculate the "ei...