268 search results for "PCA"

Color Palettes in RGB Space

June 20, 2012
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Color Palettes in RGB Space

Introduction I've recently been interested in how to communicate information using color. I don't know much about the field of Color Theory, but it's an interesting topic to me. The selection of color palettes, in particular, has been a topic I've been faced with lately. I downloaded 18 different sequential color palettes from Cynthia Brewer's

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

June 13, 2012
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Estimation of hydraulic conductivity and its uncertainty from grain-size data using GLUE and artificial neural networks.

AbstractVarious approaches exist to relate saturated hydraulic conductivity (Ks) 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 Ks prediction. Besides the predictive capacity of the methods,...

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

May 16, 2012
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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....

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Visualising the Path of a Genetic Algorithm

April 23, 2012
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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...

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Customising vegan’s ordination plots

April 11, 2012
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Customising vegan’s ordination plots

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 →

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Customising vegan’s ordination plots

April 11, 2012
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Customising vegan’s ordination plots

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 do this a lot is not really a reflection on the quality of the plot() methods...

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Ruin probability and infinite time

March 27, 2012
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Ruin probability and infinite time

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...

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Julia functions for the Rmath library

March 26, 2012
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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...

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Visualization in regression analysis

February 23, 2012
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Visualization in regression analysis

Visualization is a key to success in regression analysis. This is one of the (many) reasons I am also suspicious when I read an article with a quantitative (econometric) analysis without any graph. Consider for instance the following dataset, obtai...

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Maps with R (III)

February 23, 2012
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Maps with R (III)

In my previous posts (1 and 2) I wrote about maps with complex legends but without any kind of interactivity. …Continuar leyendo »

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