2730 search results for "GIS"

Pilot Study: Small Town Land Surface Temperature

October 11, 2012
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Pilot Study: Small Town Land Surface Temperature

Introduction Zhang and Imhoff (2010)  pdf here utilized NLCD impervious surface area (ISA), Olson biomes, and MODIS Land Surface temperature (LST) to estimate the magnitude of UHI in large cities across the US.  Peng  employed a   similar approach in studying 419 large cities ( population greater than 1m ) around world. Peng’s work suggests a limit

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From holey polygons to convex hulls

October 11, 2012
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From holey polygons to convex hulls

I only rarely have the occasion to need the convex hull of a set of points, but I love chull(), so I’d like to share an example of how to use it. This Gist also offers a pretty straightforward application of the Split-Apply-Combine strategy (see...

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Simple marimekko/mosaic plots

October 10, 2012
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Simple marimekko/mosaic plots

I don’t really care for the name “marimekko” or “mosaic,” but I do like this type of plot as a means of illustrating proportions in nested categorical data, or as an alternative to the parallel time series plots discussed...

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Making Color Ramps in Matlab

October 9, 2012
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When visualizing an array of data in a heatmap, a good color map makes a world of difference.Thanks to my work in 'omics (i.e. transcriptomics - microarrays and RNASeq) I've looked at a lot of heatmaps over the past couple of years, and generated quite...

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Age-Period-Cohort models and the decline of violence

October 9, 2012
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Age-Period-Cohort models and the decline of violence

Ever since the end of the Mexican Revolution and the Cristero War violence in Mexico inched down in fits and starts from a high of about 60 homicides per 100,000 people to its lowest level sometime during the middle of the last decade (there's some uncertainty about the number of homicides in...

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Conditional Colors and Shapes in plot() with ifelse()

October 9, 2012
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Conditional Colors and Shapes in plot() with ifelse()

Here’s an example of how to color your plot shapes and pch using an ifelse() statement. Ifelse() is handy as it creates an easy way to branch a function. The syntax is: ifelse(logical.condition, option1, option2). Meaning, if the logical condi...

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Upcoming events

October 9, 2012
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Upcoming events

Featured I’ll be leading two courses in the near future: Value-at-Risk versus Expected Shortfall 2012 October 30-31, London. 30th: “Addressing the critical challenges and issues raised by the Basel proposal to replace VaR with Expected Shortfall” 31st: “Variability in Value-at-Risk and Expected Shortfall” led by Patrick Burns Details at CFP Events. Finance with R Workshop … Continue reading...

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Two ways that correlation and stepwise regression can give different results

October 8, 2012
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In general, a correlation test is used to test the association between two variables (y and z). However, if there is a third variable (x) that might be related to z or y, it makes...

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Functions for plotting and getting Greek in labels

October 8, 2012
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Functions for plotting and getting Greek in labels

The problem: We often want to plot data and assign plot attributes based on characteristics of the data. For example, if we have a group of students with the following IQs, we might want to indicate who is an outlier in the statistical sense. I like...

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How to read BSMAP methylation ratio files into R via methylKit

October 5, 2012
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BSMAP is an aligner for bisulfite sequencing reads. It outputs aligned reads as well as methylation ratios per base (via methratio.py script). The methylation ratios can be read into R via methylKit package and regular methylKit analysis can ...

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