284 search results for "PCA"

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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Big-Data PCA: 50 years of stock data

June 17, 2011
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Big-Data PCA: 50 years of stock data

In this post, Revolution engineer Sherry LaMonica shows us how to use the RevoScaleR big-data package in Revolution R Enterprise to do principal components analysis on 50 years of stock market data -- ed. Principal components analysis, or PCA, seeks to find a set of orthogonal axes such that the first axis, or first principal component, accounts for as...

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Principal Component Analysis (PCA) vs Ordinary Least Squares (OLS): A Visual Explanation

September 16, 2010
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Principal Component Analysis (PCA) vs Ordinary Least Squares (OLS): A Visual Explanation

Over at stats.stackexchange.com recently, a really interesting question was raised about principal component analysis (PCA). The gist was “Thanks to my college class I can do the math, but what does it MEAN?” I felt like this a number of times in my life. Many of my classes were focused on the technical implementations they kinda

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Using R and r.mapcalc (GRASS) to Estimate Mean Topographic Curvature

August 3, 2010
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Using R and r.mapcalc (GRASS) to Estimate Mean Topographic Curvature

Recently I was re-reading a paper on predictive soil mapping (Park et al, 2001), and considered testing one of their proposed terrain attributes in GRASS. The attribute, originally described by Blaszczynski (1997), is the distance-weighted mean differe...

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Tutorial: Principal Components Analysis (PCA) in R

May 20, 2010
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Found this tutorial by Emily Mankin on how to do principal components analysis (PCA) using R. Has a nice example with R code and several good references. The example starts by doing the PCA manually, then uses R's built in prcomp() function to do the s...

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Compcache on Ubuntu on Amazon EC2

May 4, 2010
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Compcache on Ubuntu on Amazon EC2

The following fully-automatic Bash script downloads, compiles, and initializes compcache version 0.6.2 on Ubuntu Karmic Koala (9.10). This script creates two swaps with a maximum of 4GB uncompressed size each. Two swaps are used to take advantage of 2 CPUs (or CPU cores in a multicore CPU). Compcache is a fascinating memory compression system. The

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Bias in Observational Studies – Sensitivity Analysis with R package episensr

April 18, 2015
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Bias in Observational Studies – Sensitivity Analysis with R package episensr

When it’s time to interpret the study results from your observational study, you have to estimate if the effect measure you obtained is the truth, if it’s due to bias (systematic error, the effect measure’s precision), or if it’s due to chance (random error, the effect measure’s validity) (Rothman and Greenland, 2008, pp115-134). Every study … Continue reading...

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Parallel R with BatchJobs

March 28, 2015
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Parallel R with BatchJobs

Parallelizing R with BatchJobs – An example using k-means Gord Sissons, Feng Li Many simulations in R are long running. Analysis of statistical algorithms can generate workloads that run for hours if not days tying up a single computer. Given the amount of time R programmers can spend waiting for results, getting acquainted parallelism makes

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Growing some Trees

March 18, 2015
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Growing some Trees

Consider here the dataset used in a previous post, about visualising a classification (with more than 2 features), > MYOCARDE=read.table( + "http://freakonometrics.free.fr/saporta.csv", + header=TRUE,sep=";") The default classification tree is > arbre = rpart(factor(PRONO)~.,data=MYOCARDE) > rpart.plot(arbre,type=4,extra=6) We can change the options here, such as the minimum number of observations, per node > arbre = rpart(factor(PRONO)~.,data=MYOCARDE, + control=rpart.control(minsplit=10)) > rpart.plot(arbre,type=4,extra=6) or...

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How to Make a Histogram with ggplot2

March 12, 2015
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How to Make a Histogram with ggplot2

In our previous post you learned how to make histograms with the hist() function. You can also make a histogram with ggplot2, “a plotting system for R, based on the grammar of graphics”. This post will focus on making a Histogram With ggplot2. Want to learn more? Discover the DataCamp tutorials. Step One. Check That The post

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