Pca and R

Estimation of hydraulic conductivity and its uncertainty from grain-size data using GLUE and artificial neural networks.

June 13, 2012

Abstract
Various approaches exist to relate saturated hydraulic conductivity (K_s) to grain-size data. Most methods use a single grain-size parameter and hence omit the information encompassed by the entire grain-size distribution. This study compares two data-driven modelling methods—multiple linear regression and artificial neural networks—that use the entire grain-size distribution data as input for K_sprediction. Besides the predictive capacity of the methods,...

PCA and ggplot2 to recognise gestures (via David…

June 12, 2012

By Hadley

PCA and ggplot2 to recognise gestures (via David Chudzicki’s Blog: Visualizing ChaLearn Gestures Test Data)

Stepping Outside My Open-Source Comfort Zone: A First Look at Golden Helix SVS

May 16, 2012

By Stephen Turner

Stepping Outside My Open-Source Comfort Zone: A First Look at Golden Helix SVS

I'm a huge supporter of the Free and Open Source Software movement. I've written more about R than anything else on this blog, all the code I post here is free and open-source, and a while back I invited you to steal this blog under a cc-by-sa license....

Visualising the Path of a Genetic Algorithm

April 23, 2012

By simonraper

Visualising the Path of a Genetic Algorithm

We quite regularly use genetic algorithms to optimise over the ad-hoc functions we develop when trying to solve problems in applied mathematics. However it’s a bit disconcerting to have your algorithm roam through a high dimensional solution space while not being able to picture what it’s doing or how close one solution is to another. … Continue reading...

Customising vegan’s ordination plots

April 11, 2012

By ucfagls

As a developer on the vegan package for R, one of the most FAQs is how to customise ordination diagrams, usually to colour the sample points according to an external grouping variable. Now, just because we get asked how to … Continue reading →

Ruin probability and infinite time

March 27, 2012

By arthur charpentier

A couple of weeks ago, I had a discussion with a practitioner, working in some financial company, about ruin, and infinite time. And it remind me a weird result. Well, not a weird result, but a result I found disturbing, at first, when I was a stud...

Julia functions for the Rmath library

March 26, 2012

By Douglas Bates

1.1 Signatures of the d-p-q-r functions in libRmath Users of R are familiar with the functions for evaluating properties of and for sampling from probability distributions, the so-called d-p-q-r functions. The designation d-p-q-r reflects the fact t...

PCA for NIR Spectra_part 006: "Mahalanobis"

February 28, 2012

By jrcuesta

PCA for NIR Spectra_part 006: "Mahalanobis"

Outliers have an important influence over the PCs, for this reason they must be detected and examinee.We have just the spectra without lab data, and we have to check if any of the sample spectra is an outlier ( a noisy spectrum, a sample which belongs ...

PCA for NIR Spectra_part 005: "Reconstruction"

February 27, 2012

By jrcuesta

PCA for NIR Spectra_part 005: "Reconstruction"

We saw how to plot the raw spectra (X), how to calculate the mean spectrum, how to center the sprectra (subtracting the mean spectrum from every spectra of the original matrix X). After that we have developed the PCAs with the NIPALS algorithm, getting...

PCA for NIR Spectra_part 004: "Projections"

February 26, 2012

By jrcuesta

PCA for NIR Spectra_part 004: "Projections"

This plot in 2D, help us to decide the number of PCs, it is easy to create in R, once we have discompose the X matrix into a P matrix (loadings) and a T matrix (scores).For this plot, we just need the T matrix.> CPs<-seq(1,10,by=1)> matp...