4161 search results for "git"

A pathological glm() problem that doesn’t issue a warning

May 1, 2013
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A pathological glm() problem that doesn’t issue a warning

I know I have already written a lot about technicalities in logistic regression (see for example: How robust is logistic regression? and Newton-Raphson can compute an average). But I just ran into a simple case where R‘s glm() implementation of logistic regression seems to fail without issuing a warning message. Yes the data is a Related posts:

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Volatility Regimes: Part 1

Volatility Regimes: Part 1

This is a ‘do over’ of a project I started while at my former employer in the fall of 2012. I presented part 1 of this framework at the FX Invest West Coast conference on September 11, 2012. I have made some changes and expanded the analysis since then. Part 2 is complete and will follow this post in...

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Le Monde puzzle [#818]

April 30, 2013
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Le Monde puzzle [#818]

The current puzzle is as follows: Define the symmetric of an integer as the integer obtained by inverting the order of its digits, eg 4321 is the symmetric of 1234. What are the numbers for which the square is equal to the symmetric of the square of the symmetric? I first consulted stackexchange to find

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What the BBC isn’t telling you

April 30, 2013
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What the BBC isn’t telling you

Yesterday Gareth pointed me to this article on the BBC website. The underlying story has to do with Meredith Kercher's murder and the subsequent trial involving mainly her flat-mate Amanda Knox, in Perugia (Italy). As often in these grue...

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Has R-help gotten meaner over time? And what does Mancur Olson have to say about it?

April 30, 2013
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Has R-help gotten meaner over time? And what does Mancur Olson have to say about it?

R users know it can be finicky in its requirements and opaque in its error messages. The beginning R user often then happily discovers that a mailing list for dealing with R problems with a large and active user base, R-help, has existed since 1997. Then, the beginning R user wades into the waters, asks… Continue reading →

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A Brief Tour of the Trees and Forests

April 29, 2013
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A Brief Tour of the Trees and Forests

Tree methods such as CART (classification and regression trees) can be used as alternatives to logistic regression. It is a way that can be used to show the probability of being in any hierarchical group. The following is a compilation of many of the key R packages that cover trees and forests.  The goal here

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Poor man’s integration – a simulated visualization approach

April 29, 2013
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Poor man’s integration – a simulated visualization approach

Every once in a while I encounter a problem that requires the use of calculus. This can be quite bothersome since my brain has refused over the years to retain any useful information related to calculus. Most of my formal training in the dark arts was completed in high school and has not been covered

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d3 <- R with rCharts and slidify

April 29, 2013
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I believe that the NY Times interactive feature 512 Paths to the White House is one of the best visualizations of all time.  It is even better when we have details on the process of creating this marvel.   Although the graphic is not suited for other data sources (please tell me if this is not...

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Stats in the Court Room Hands on Tutorial

April 29, 2013
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I got intrigued by the numbers presented in this news article talking about the re-trial in the Amanda Knox case. The defendants, accused and initially convicted of murder, were acquitted in the appeal's instance when the judge ruled that the forensic evidence was insufficiently conclusive. The appeals judge ignored the forensic scientist's advice to retest a DNA sample,...

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How to change the alpha value of colours in R

April 29, 2013
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How to change the alpha value of colours in R

Often I like to reduce the alpha value (level of transparency) of colours to identify patterns of over-plotting when displaying lots of data points with R. So, here is a tiny function that allows me to add an alpha value to a given vector of colours, e.g. a RColorBrewer palette, using col2rgb and rgb, which has...

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