3125 search results for "gis"

Why are Birds Dinosaurs?

June 9, 2013
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Why are Birds Dinosaurs?

Month after month, one of the most popular posts on the Paleocave blog is the How to Read a Cladogram post I did some time ago. I always intended to follow it up with more cladistic fun. So, hold onto your butts, we’re going to let the dinosaurs loose. Birds are dinosaurs. We’ve all heard

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Quartiles, Deciles, and Percentiles

June 9, 2013
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The measures of position such as quartiles, deciles, and percentiles are available in quantile function. This function has a usage,where:x - the data pointsprob - the location to measurena.rm - if FALSE, NA (Not Available) data points are not ignoredna...

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Quick and Simple D3 Network Graphs from R

June 8, 2013
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Quick and Simple D3 Network Graphs from R

Sometimes I just want to quickly make a simple D3 JavaScript directed network graph with data in R. Because D3 network graphs can be manipulated in the browser–i.e. nodes can be moved around and highlighted–they're really nice for data exploration. They're also really nice in HTML presentations. So I put together a...

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Mean and Median

June 8, 2013
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Mean in R is computed using the function mean. Consider the scores of 20 MSU-IIT students in Stat 101 exam with a hundred items: 70, 78, 66, 65, 50, 53, 48, 88, 95, 80, 85, 84, 81, 63, 68, 73, 75, 84, 49, and 77. Compute and interpret the mean and medi...

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Matrix Operations

June 8, 2013
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Matrix manipulation in R are very useful in Linear Algebra. Below are lists of common yet important functions in dealing operations with matrices:Transpose - tMultiplication - %*%Determinant - detInverse - solve, or ginv of MASS libraryEigenvalues and ...

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Data Class Conversion

June 6, 2013
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Data in R can be converted from one class to the other. The function is prefixed with as. then followed by the name of the data class that we wish to convert to. Data class in R are the following:numeric - as.numericvector - as.vectorcharacter - as.cha...

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How likely is the NSA PRISM program to catch a terrorist?

June 6, 2013
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How likely is the NSA PRISM program to catch a terrorist?

Recent revelations about PRISM, the NSA’s massive program of surveillance of civilian communications have caused quite a stir. And rightfully so, as it appears that the agency has been granted warrantless direct access to just about any form of digital communication engaged in by American citizens, and that their access to such data has been

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Feature Selection 3 – Swarm Mentality

June 6, 2013
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Feature Selection 3 – Swarm Mentality

"Bees don't swarm in a mango grove for nothing. Where can you see a wisp of smoke without a fire?" - Hla Stavhana In the last two posts, genetic algorithms were used as feature wrappers to search for more effective subsets of predictors. Here, I will do the same with another type of search algorithm: particle swarm optimization....

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Intro to Parallel Random Number Generation with RevoScaleR

June 6, 2013
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Intro to Parallel Random Number Generation with RevoScaleR

by Joseph Rickert Random number generation is fundamental to doing computational statistics. As you might expect, R is very rich in random number resources. The R base code provides several high quality random number generators including: Wichmann-Hill, Marsaglia-Multicarry, Super-Duper, Mersenne-Twister, Knuth-TAOCP-2002 and L’Ecuyer-CMRG. (See Random for details.) And, there are at least three packages, rspring, rlecuyer, and rstream for...

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Inputting Data in Matrix Format

June 6, 2013
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Matrix in R is formed using matrix, rbind, or cbind function. These functions have the following descriptions:matrix - used to transform a concatenated data into matrix form of compatible dimensions. rbind - short for row bind, that binds a conca...

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