2121 search results for "twitter"

Counting Clusters

March 13, 2011
By
Counting Clusters

Given a set of numerical datapoints, we often want to know how many clusters the datapoints form. Two practical algorithms for determining the number of clusters are the gap statistic and the prediction strength. Gap Statistic The gap statistic algorithm … Continue reading →

Read more »

Legendary Plots

March 12, 2011
By
Legendary Plots

I was recently pointed in the direction of a thermal comfort model by the engineering company Arup (p27–28 of this pdf). Figure 3 at the top of p28 caught my attention. It’s mostly a nice graph; there’s not too much junk in it. One thing that struck me was that there is an awful lot

Read more »

A new series of mishaps

March 12, 2011
By
A new series of mishaps

Following the slight difficulties of last week, I had a hard week on the computer front: indeed, on Monday, I received my 2007 macbook from the repair shop, with a new video card, courtesy of Apple. Unfortunately, this started a series of problems. First, the old macbook stopped recognizing the NVIDIA video and, while it

Read more »

A quick look at #march11 / #saudi tweets

March 12, 2011
By
A quick look at #march11 / #saudi tweets

Well, so much for that #march11 #Saudi day of rage.  Whether it was really the "tempest in a teacup" that  Prince Al-Waleed suggested on CNBC (video below, transcript here) or not, the oil complex and Saudi markets seem to have shrugged … Continue reading →

Read more »

Special issue of TOMACS

March 9, 2011
By
Special issue of TOMACS

TOMACS (ACM Transactions on Modeling and Computer Simulation) is launching a call for paper submission. The special topic is Monte Carlo Methods in Statistics and Arnaud Doucet and myself are the special issue editors. Here are the details.: Over the last two decades Monte Carlo methods have attracted much attention from statisticians as they provide

Read more »

In case you missed it: February Roundup

March 9, 2011
By

In case you missed them, here are some articles from February of particular interest to R users. Revolution R Enterprise 4.2 is now available to subscribers, and for free download to academics. A brief report from the Strata: Working with Data conference, and a comprehensive review from Ted Leung. A profile of prolific R contributor, Dirk Eddelbuettel. A list...

Read more »

In case you missed it: January Roundup

March 8, 2011
By

Catching up on roundups today. February roundup will follow soon, but in the meantime enjoy this trip down memory lane - DS. In case you missed them, here are some articles from January of particular interest to R users. Revolution Analytics is now offering annual sponsorship grants for local R user groups worldwide. Issue 2 of the R Journal...

Read more »

Alabama is a foreign country

March 7, 2011
By
Alabama is a foreign country

Faculty and students of Iowa State University Department of Statistics published online an analysis of the data on 2009 distributions of the US Stimulus funds, aka the Recovery And Reinvestment Act. (The analysis was published in March last year as part of the Design for America competition, but I only recently came across it.) The analyses and associated charts...

Read more »

Factor models of variance in finance

March 7, 2011
By
Factor models of variance in finance

In “What the hell is a variance matrix?” I talked about the basics of variance matrices and highlighted challenges for estimating them in finance.  Here we look more deeply at the most popular estimation technique. Models for variance matrices The types of variance estimates that are used in finance can be classified as: Sample estimate … Continue reading...

Read more »

More on logging the outcome

March 4, 2011
By
More on logging the outcome

This one does my head in. I do it fairly regularly, lots of people do, but I find everytime it comes to interpreting the results I have to slow it right down and go step by step. Answer: When you log the outcome, then on the original scale, for all else constant, Y will be

Read more »