2722 search results for "gis"

When Russell 2000 is Low Vol

October 1, 2012
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When Russell 2000 is Low Vol

Continuing in my exploration of the Russell 2000 (Russell 2000 Softail Fat Boy), I thought I would try to approach the topic with a low volatility paradox mindset.  Since 2005, beta of the Russell 2000 compared to the S&P 500 has exceeded 1.2 ...

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Level fit summaries can be tricky in R

October 1, 2012
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Level fit summaries can be tricky in R

Model level fit summaries can be tricky in R. A quick read of model fit summary data for factor levels can be misleading. We describe the issue and demonstrate techniques for dealing with them.When modeling you often encounter what are commonly called categorical variables, which are called factors in R. Possible values of categorical variables Related posts:

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Making random, equally-sized partitions

October 1, 2012
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Making random, equally-sized partitions

Sometimes, as with cross-validation, one needs to generate k partitions, each with an equal number of observations. There are probably an infinite number of ways this could be done in R, but the Gist below illustrates one way to do it in four lines, w...

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Quantifying student feedback using Org mode and R

September 30, 2012
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Quantifying student feedback using Org mode and R

As the term has progressed, my LSM2241 lectures are getting more consistent. I’m aiming to use 45 slides for what is officially a two hour lecture, although in reality it lasts about 90 minutes. We take a break at about 50 … Continue reading →

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Padding integers for use in filenames

September 29, 2012
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Padding integers for use in filenames

If you’ve ever written code that generates a whole whack of files, you may have came across the following problem when processing them. Using a naming convention wherein files are numbered will  gum up any ordering which is based on string sorting (ls, for example). What you end up with is something like this: Which

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Optimal seriation for your matrices

September 28, 2012
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Optimal seriation for your matrices

In our previous post, we used a quick-and-dirty method for ordering the axes on our heatmap. It has been pointed out to me that There is a Package for That (which is my nominee for a new slogan for R — not that it needs a slogan). seriation offe...

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Histogram + Density Plot Combo in R

September 27, 2012
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Histogram + Density Plot Combo in R

Plotting a histogram using hist from the graphics package is pretty straightforward, but what if you want to view the density plot on top of the histogram? This combination of graphics can help us compare the distributions of groups.Let's use...

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The simplest Species Distribution Model in OpenBUGS & R

September 27, 2012
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This post demonstrates the simplest Species Distribution Model based on logistic regression for presence/absence data. I heavily simplified the example from Kéry (2010): Introduction to WinBUGS for Ecologists, Chapter 20.Read more →

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Continuous dispersal on a discrete lattice

September 27, 2012
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Continuous dispersal on a discrete lattice

Dispersal is a key process in many domains, and particularly in ecology. Individuals move in space, and this movement can be modelled as a random process following some kernel. The dispersal kernel is simply a probability distribution describing the distance travelled in a given time frame. Since space is continuous, it is natural to use

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Simplest possible heatmap with ggplot2

September 27, 2012
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Simplest possible heatmap with ggplot2

Featuring the lovely “spectral” palette from Colorbrewer. This really just serves as a reminder of how to do four things I frequently want to do: Make a heatmap of some kind of matrix, often a square correlation matrix Reorder a factor vari...

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