295 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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Seattle’s Fremont Bridge Bicyclists Again in the News

August 2, 2015
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Seattle’s Fremont Bridge Bicyclists Again in the News

Back in 2013, David Smith had done analysis of bicycle trips across Seattle’s Fremont bridge. More recently, Jake Vanderplas (creator of Python’s very popular Scikit-learn package) wrote a nice blog post on “Learning Seattle Work habits from bicycle counts” at … Continue reading →

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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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