Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Compare cell phone plans using Wirefly's innovative plan comparison tool ×

Comment Re:Bad plots (Score 1) 247

My strengths are definitely on the electronics / software side; I did fine in stats in high school, but haven't done anything significant since. Thanks for the notes on tests of randomness.

If you'd like to chip in, all the data is available on github. I closed my post with a call for statisticians to come along and do a better analysis; maybe you're it! (: Glad to help you extract the roll sequence numbers if using summarize.py to pull it out of each die's summary.json is not your thing.

And yeah, that first chart was frustrating. The easiest tool to hand was Google Spreadsheets, but the choices are side-by-side bar graph and line + bar graph. As you said, clealry the wrong tool for the job, but at least it gets the point across. But that too is in github along with its source CSV if you'd like to make a better one!

Comment Re:Summary is not an abstract (Score 1) 247

I actually get frustrated with clickbait titles and summaries, so I wanted to pack as much information into the summary as possible. My goal was to intrigue people by telling them what they could hear more about, rather than luring them by leaving out interesting detail.

So yes, I was trying to write the abstract of a paper, more or less. :)

Comment Re:I use the salt water test (Score 1) 247

I haven't tried a floating test; that'd be interesting to compare.

I did measure the diameters of a handful of the dice, though, and found some correlation with die behavior. markfickett.com/dice#geometry for more on that.

Do you think the dice float with one side up because of bubbles inside them, or something else? I wonder how a die that's egg-shaped or otherwise irregular in shape (but not mass distribution) would behave in a float test.

Comment Re:Didn't need this elaborate set up (Score 1) 247

I think it depends on what you have on hand. I had a microcontroller and a servo motor, but not a woodshop or a reliable DC motor. I like the simplicity of mechanical systems though, avoiding computer control.

My guess is it would also be hard to make the motor and the timer coordinate precisely enough, over 3000 rolls. You could add some interconnect so the camera is tripped when the cam gets to the top, though.

One advantage of computer control though is in chaining the whole system together, roll + photograph + analyze. Timothy Weber actually has a video of something very similar to what I did, but with realtime analysis; unfortunately no detailed writeup yet. timothyweber.org/dieroller

Comment Re:Didn't need this elaborate set up (Score 1) 247

Waiting for the dice to roll definitely was the longest step. But I also ran out of dice (even though now I have 5 seven-die sets, and three assortments of d20s!), and was making graphs or improving the software (or sleeping / going to work) while the dice ran. So even though it's the right target for optimizing the overall process (as the longest part), there wasn't a lot of pressure to optimize.

Also, I got away with a pretty simple heuristic for finding the die in the picture; just looking for an area that changed and using a simple flood-fill to identify the area. (That part was just using PIL, not any OpenCV fanciness. More at markfickett.com/dice/#cropping.) Extracting multiple separate dice would make that step much harder, especially since you'd need to not only extract them but identify which die is which.

Comment Re:One: (Score 1) 247

What do you think of my comparison of different numbers of rolls out of the sequence? I actually started with 8k rolls. But comparing (computer-selected pseudo-)random subsamples of the roll sequence, using 2k, 3k, or 8k all looked about the same, whereas using 100 or 1000 rolls was quite different. markfickett.com/dice#numrolls

I actually did some investigation of p-values along the way. For example the Koplow dice I tested, which were slightly fairer than average among the 19 d20s I ran, all have p 0.001 for their 3001 roll datasets. But what I want to say isn't "with X% confidence, this die is not fair". I basically know that to start with. I want to know "how does this die behave?"

Comment Re:I disagree (Score 1) 247

I would want a 100 of each ...

Me too! (: Unfortunatley neither my camera's mechanical shutter nor my budget for recreational dice purchases supports that whim. But I think the handful I tested still proved interesting.

Now, if someone wants to donate some larger bags of dice, I might try to port this to a Pi and its camera module (with an electronic shutter). And maybe add a mechanism for swapping out one die for the next. That's starting to sound like another serious project!

Submission + - Experimental Study of 29 Polyhedral Dice Using Rolling Machine, OpenCV Analysis (markfickett.com)

enFi writes: All dice are slightly unfair; automating 3k rolls x 29 dice allows detailed exploration. For example: GameScience claims their d20s are fairest, and actually has the fairest die in the study. Chessex d20s are consistently mid-range and all favor the same numbers; Wiz Dice d20s are highly variable (some rival GameScience). Shape differences measurable with calipers account for some of the larger observed differences, but not everything. Read the details for graphs, a video of the Arduino-powered rolling machine, and an explanation of using OpenCV to sort die rolls.

(Disclaimer: I'm the author.)

Comment Re:Not your problem. (Score 1) 619

[...] you're poisoning the spam filter rules, and making it harder for the filter to distinguish between legitimate and truly spammy email.

Worse, if you're doing it on a webmail client, you're essentially poisoning the communal filter.

Not necessarily. I hope a good spam filter takes the recipient into account as context. E-mail from Verizon to me? Spam. E-mail from Verizon to my co-worker with FiOS? Maybe not. E-mail addressing Mr. Smith delivered to neo@? More spam.

Submission + - Induction Heat & Levitation Coil Floats Molten (inductionheatertutorial.com)

enFi writes: "Arduino forum user imsmooth posts the details of making an induction heater (such as to prepare metal for forging), and then modifying the coil and upping the power to 10kW so it can melt small pieces of copper or steel and levitate the molten blob. The video in the post is impressively cool. (What could go wrong?)"
Firefox

Submission + - Firefox 4.0 (Final) Now Available For Download (conceivablytech.com)

An anonymous reader writes: It isn't officially announced yet, but the download link for Firefox 4 (final) is already live. If you have downloaded Firefox 4 RC2 (released last Friday), you already run the final code, according to Mozilla. The official launch of the new browser is still scheduled for tomorrow, March 22.

Slashdot Top Deals

RAM wasn't built in a day.

Working...