Viewing profile — ltjohnson

This is correct. Sadly, the first paragraph of the article contains some glaring errors. "For Markov chains to be effective the current state has to be dependent on the previous st…

Most statisticians have their own definition of fat-tailed, I like the definition you linked to (polynomial decay), but it is not universally accepted/known. These fat-tailed distr…

I also used to work for Erik's (dinkytown location). That was the gross margin on bikes, which I'm pretty sure means (sale price - purchase price)/(purchase price). Correct me if I…

I sort of addressed this in my above comment. Success in academic research, like success in startups, is more dependent on determination than intelligence.

I'm finishing up my PhD this year (haven't set a defense day yet, but I'm aiming for June at this point), and finishing a dissertation requires piles of determination. What I came …

Possibly. R is really great at doing "fancy" statistical analyses. It's very lousy at doing things like text manipulation. When I have a project that needs some text manipulation o…

No, but I can give some suggestions. It would help to know what you want to do. First of all, you need to decide if you want a language reference, or an application guide, as R boo…

I am a statistician that does both research and applied work. I use R for three reasons: (1) It's Free Software; (2) It's a programming language; (3) Other statisticians use it so …

You're right, reading the paper that way, they are trying to detect a change in convergence rate from 5% to 5.25%, I was confused by the use of % in two separate contexts in the sa…

122,000 seemed absurdly large to me so I just looked up the paper you reference [1]. It looks like there is a calculation error in the paper. The formula they use is n = 16 σ^2 / Δ…

Just signed up. But, my main areas of expertise (statistics, e.g. data analysis or mining, modeling or forecasting, designing and analyzing experiments, ...) don't mesh well with y…

You gotta do what you gotta do, but your example probably doesn't do what you want in R. > system.time(vec1 My computer takes .2 seconds to generate the million random normals and …

I've added some examples to my above comment. My example is perhaps a little closer to 'median(x <- 10)' than you were asking for, but I think it illustrates the point that using '…

Using ' The operator ‘ That being said, some R community members still use '=' for assignment, but it's frowned upon. It certainly annoys me when I see it in R code. Simple example…

Speaking as an almost not-amateur (finishing my PhD this year, and working on getting a faculty job), you're both right. Logically, there's nothing wrong with proof by contradictio…

I'm not interpreting your comment as flippant. :) In terms of shortcuts, that would depend on what they were. Some are fine, others are not. E.g. 'borrowing' answers from other stu…

I'm a 5th year PhD student who is teaching a large (80 student) section of a course, this is the 4th course I've taught. I've also taken plenty of exams as a student, and they are …

I'll start by saying that I'm not trolling. Using conditional probability, or bayes theorem to calculate a conditional probabilitiy, does not make something bayesian analysis. I ha…