Posts Tagged ‘ "R" Chemometrics ’

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

February 2, 2012
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"R": Plotting the spectra (Gasoline) – 002

"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)")>...

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

February 1, 2012
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"R": Looking at the Data (Gasoline) – 001

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)

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

January 1, 2012
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NIPALS: Principal Components Analysis with "R" (Part: 002)

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...

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IRIS Flower Data Set (R-003)

December 19, 2011
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IRIS Flower Data Set (R-003)

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 ...

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IRIS Flower Data Set (R-002)

December 17, 2011
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IRIS Flower Data Set (R-002)

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...

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IRIS Flower Data Set (R-001)

December 17, 2011
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IRIS Flower Data Set (R-001)

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...

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Pairs for the "P" (loadings) matrix

December 12, 2011
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Pairs for the "P" (loadings) matrix

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...

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

December 7, 2011
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Principal Components Analysis with "R" (Part: 001)

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...

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PCA file calculation with "R".

December 5, 2011
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PCA file calculation with "R".

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...

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