294 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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R tutorial on the Apply family of functions

July 28, 2015
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R tutorial on the Apply family of functions

Introduction In our previous tutorial Loops in R: Usage and Alternatives , we discussed one of the most important constructs in programming: the loop.  Eventually we deprecated the usage of loops in R in favor of vectorized functions. In this post we highlight some of the most used vectorized functions: the apply functions. In the present post we show the use The post

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Pull the (character) strings with stringi 0.5-2

June 23, 2015
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A reliable string processing toolkit is a must-have for any data scientist. A new release of the stringi package is available on CRAN (please wait a few days for Windows and OS X binary builds). As for now, about 850…Read more ›

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Tips & Tricks 9: Shape Changes and Hypothetical Shapes

June 18, 2015
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Tips & Tricks 9: Shape Changes and Hypothetical Shapes

Geomorph users,This month's tips and tricks was prompted by a user email from Tim Astrop, thanks Tim!How can I create a hypothetical shape representing a point in shape space?Today we will use some relatively simple R code to create a shape based on position in a Principal Component (PC) shape space and visualise this shape as a change from the mean using...

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Interactive maps for the web in R

May 15, 2015
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Interactive maps for the web in R

Static MapsIn the last post I showed how to download economic data from the World Bank's website and create choropleth maps in R (Global Economic Maps).In this post I want to focus more on how to visualize those maps.Sp PackageProbably the simplest way...

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