2602 search results for "gis"

Flag space: a scatter plot of raster images

October 16, 2012
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Flag space: a scatter plot of raster images

(Click for a bigger version) I’m not sure when plotting raster images in an R scatter plot will end up being useful. It’s not something I expect to need to do in my day-to-day research, and I think in general probably adds more complexity ...

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Not Much of a Grand Finale. What if We Go To 0?

October 15, 2012
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Not Much of a Grand Finale. What if We Go To 0?

When I ask the question “What if the US 10 year goes to 0?", most do not know the effect, the catalyst, or if 0 has ever happened before.  The math is fairly simple to do in Excel or with an old-school calculator, but let’s use RQuantLib to do...

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Gale-Shapley Deferred Acceptance in R

October 15, 2012
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Gale-Shapley Deferred Acceptance in R

In honor of today’s announcement of the Nobel Prize for Roth and Shapley, I found an illustration of the deferred acceptance algorithm from 1962 in R. Credit for the code goes to the blogger at Letters from London, and I’ve included a Gi...

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Banking to n degrees

October 15, 2012
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Banking to n degrees

As often happens, I have learned of a technique just as it is being called into question. In this case, the technique is changing the aspect ratio of a line plot such that the typical slope of each segment is 45° (see), a rule of thumb which has bee...

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Fixing non positive definite correlation matrices using R

Problem When a correlation or covariance matrix is not positive definite (i.e., in instances when some or all eigenvalues are negative), a cholesky decomposition cannot be performed. Sometimes, these eigenvalues are very small negative numbers and occur due to rounding or due to noise in the data. In simulation studies a known/given correlation has to be imposed on an input...

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Dark matter benchmarks: All over the map

October 14, 2012
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Dark matter benchmarks: All over the map

The three benchmark algorithms for predicting the location of dark matter halos are, for the most part, all over the map. Most of the test skies look something like this: There are, however, some skies with rather strong halo signals that get a decent amount of agreement: The Lenstool MLE algorithm is the current state

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Observing Dark Worlds – Visualizing dark matter’s distorting effect on galaxies

October 13, 2012
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Observing Dark Worlds – Visualizing dark matter’s distorting effect on galaxies

Some people like to do crossword puzzles. I like to do machine learning puzzles. Lucky for me, a new contest was just posted yesterday on Kaggle. So naturally, my lazy Saturday was spent getting elbow deep into the data. The training set consists of a series of ‘skies’, each containing a bunch of galaxies. Normally,

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How to choose the right *apply function

October 13, 2012
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How to choose the right *apply function: This is an amazing stackoverflow answer to help you decide which of the many *apply functions (apply, lapply, sapply, vapply, mapply, rapply, tapply) is appropriate for the task at hand. I’m planning on doing...

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Using cairographics with ggsave()

October 12, 2012
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Using cairographics with ggsave()

Whenever possible, I try to save R graphic output in a vector format, typically pdf(). I also like to use the handy ggsave() function to do so, as it streamlines the process, and makes it easy to be consistent across formats. However, at times it is n...

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Revolution Newsletter: September/October 2012

October 11, 2012
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The most recent edition of the Revolution Newsletter is out. The news section is below, and you can read the full September/October edition (with highlights from this blog and community events) online. You can subscribe to the Revolution Newsletter to get it monthly via email. New R Courses Announced: Two new courses presented by Bob Muenchen (author of R...

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