stats

Maps without map packages

July 1, 2010 | dan

LATITUDE + LONGITUDE + OVERPLOTTING FIX = MAPS Decision Science News is always learning stuff from colleague, physicist, mathlete, and all-around computer whiz Jake Hofman. Today, it was a quick and clean way to make nice maps in R without using any map packages: just plot the latitude and longitude of your data ...
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Entropy augmentation the modulo way

June 29, 2010 | Matt Asher

Long before I had heard about the connection between entropy and probability theory, I knew about it from the physical sciences. This is most likely how you met it, too. You heard that entropy in the universe is always increasing, and, if you’re like me, that made very little ... [Read more...]

Reaching escape velocity

June 22, 2010 | Matt Asher

Sample once from the Uniform(0,1) distribution. Call the resulting value . Multiply this result by some constant . Repeat the process, this time sampling from Uniform(0, ). What happens when the multiplier is 2? How big does the multiplier have to be to force divergence. Try it and see: iters = 200 locations = rep(0,iters) [...] [Read more...]

The perfect fake

June 19, 2010 | Matt Asher

Usually when you are doing Monte Carlo testing, you want fake data that’s good, but not too good. You may want a sample taken from the Uniform distribution, but you don’t want your values to be uniformly distributed. In other words, if you were to order your sample ... [Read more...]

A different way to view probability densities

June 12, 2010 | Matt Asher

The standard, textbook way to represent a density function looks like this: Perhaps you have seen this before? (Plot created in R, all source code from this post is included at the end). Not only will you find this plot in statistics books, you’ll also see it in medical ... [Read more...]

Betting on Pi

May 31, 2010 | Matt Asher

I was reading over at math-blog.com about a concept called numeri ritardatari. This sounds a lot like “retarded numbers” in Italian, but apparently “retarded” here is used in the sense of “late” or “behind” and not in the short bus sense. I barely scanned the page, but I think ...
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How many tanks? MC testing the GTP

May 25, 2010 | Matt Asher

It’s 1943 and you work for the good guys. A handful of German tanks have been captured, and each one has a serial number. This is back when serial numbers were still presumed to come in serial, one right after the other. Given your collection of numbered tanks, and assuming ... [Read more...]

R: Dueling normals

May 18, 2010 | Matt Asher

More playing around with R. To create the graph above, I sampled 100 times from two different normal distributions, then plotted the ratio of times that the first distribution beat the second one on the y-axis. The second distribution always had a mean of 0, the mean of first distribution went from 0 ... [Read more...]
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