ltjohnson

7 ms·

1.
by ltjohnson 12y ago
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 state in some way;" This is trivially untrue. A se
2.
by ltjohnson 13y ago
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 distributions will have a variance as long as they decay fa
3.
by ltjohnson 14y ago
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'm wrong about the formula. Not included in this is 36% num
4.
by ltjohnson 15y ago
I sort of addressed this in my above comment. Success in academic research, like success in startups, is more dependent on determination than intelligence.
5.
by ltjohnson 15y ago
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 to realize is that you can't take what they say too serious
6.
by ltjohnson 16y ago
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 on the front end, I frequently use other tools (Python, vi
7.
by ltjohnson 16y ago
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 books fall into those two categories. If you have a specific t
8.
by ltjohnson 16y ago
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 it's easier for me to collaborate. There are the usual supp
9.
by ltjohnson 16y ago
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 same sentence. That being said, I think this is not a good ar
10.
by ltjohnson 16y ago
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^2. σ is the standard deviation, and Δ is the size of the
11.
by ltjohnson 16y ago
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 your categories. Have you thought about allowing users to se
12.
by ltjohnson 16y ago
You gotta do what you gotta do, but your example probably doesn't do what you want in R. > system.time(vec1 <- rnorm(1000000)) user system elapsed 0.200 0.000 0.199 My computer takes .2 seconds to generate the
13.
by ltjohnson 16y ago
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 '=' will not always have the desired result in places wh
14.
by ltjohnson 16y ago
Using '<-' is the general style of the R community. The accepted (but not universal) practice is to use '<-' for assignment and '=' in argument passing. This is a good idea because '<-' and '=' are not equivalent and '<-'
15.
by ltjohnson 16y ago
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 contradiction. As long the steps between "Assume P is true" and "theref
16.
by ltjohnson 16y ago
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 students on homework is a shortcut, but it's okay if the stud
17.
by ltjohnson 16y ago
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 still fresh in mind. I would want to know more information
18.
by ltjohnson 17y ago
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 haven't read the original report (it's on my list) but what is