Timeline for Sandbox for Proposed Challenges
Current License: CC BY-SA 3.0
19 events
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| Jun 17, 2020 at 9:03 | history | edited | CommunityBot |
Commonmark migration
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| May 6, 2015 at 21:15 | history | wiki removed | Martin EnderMod | ||
| May 3, 2015 at 15:37 | history | made wiki | Post Made Community Wiki by Martin EnderMod | ||
| Feb 4, 2015 at 13:16 | history | edited | flawr | CC BY-SA 3.0 |
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| Feb 4, 2015 at 13:04 | comment | added | flawr | Obviously we are talking about an idealized bicycle (since most bicycles also cannot drive backwards and the touching points of front and back wheel are not constant)... I will now alter the challenge so that both tracks end on the right and left side of the visible frame. This way the possible answers are right or left as a direction of travel. | |
| Feb 4, 2015 at 12:37 | comment | added | Peter Taylor | Have you ever ridden a bicycle in snow? You have to turn very carefully. As to the arrow, I can think of several nasty corner cases. The point at which I'm most confident could be where the path leaves the image, in which case only one pixel of the arrow would be inside the image bounds. The arrow could start at a point where the derivative is discontinuous, or where the path crosses back over itself, in which case there would be more than one correct answer. Given that the arrow is the same colour as one of the tracks, it could be unclear where it starts. | |
| Feb 4, 2015 at 12:28 | history | edited | flawr | CC BY-SA 3.0 |
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| Feb 4, 2015 at 12:23 | comment | added | flawr | I am sorry, I forgot to answer those. What makes you think they are impossible? As long as you manage to keep balance those tracks seem perfectly possible to me. The arrow does not need a special shape, it just must be clear for the viewer. As an arrow can only point in two different directions parallel to a line it should be obvious from the output wheter it is the right or wrong direction. The output of the confidence is also up to the participant, I thought they could directly write it to the image so we only have one output item that can easily be displayed. | |
| Feb 4, 2015 at 12:14 | comment | added | Peter Taylor | Doesn't sound much like a bicycle, but then the kind of curves you show would be impossible with a real bicycle in the snow. It would be good to edit the question with the description of your track generation model. And I don't think you've answered any of the three questions in my second comment. | |
| Feb 4, 2015 at 10:08 | history | edited | flawr | CC BY-SA 3.0 |
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| Feb 4, 2015 at 9:55 | comment | added | flawr |
Let h be the time step size. Then I calculated the distance vector of the two wheels: d(t+h):= f(t+h)-r(t) and then calculated the new position of the rear wheel: r(t+h) = f(t+h) - L/|d(t+h)| * d(t+h), where L is the distance between back and front wheel. For small enough h I thought this simulation was accurate enough. With given starting points and give f I thin r is uniquely determined. If you know how to write this as a differential equation I'd be happy to include it, but I am not sure how many of the people here can actually use them.
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| Feb 4, 2015 at 9:47 | comment | added | flawr |
Ok I will change that and do not allow ambiguous examples. I wanted the output to consist of the image input again that was altered: The program should draw an arrow on one of the lines (on an arbitrary place along the line) that represents the direction of the wheel of that path in which the wheel was going. As far as differential equations goes: I have no experience in that field. For simulation the bicycle I did following: f(t) is the position of the frontwheel at time t, similarly r(t) for the backwheel. I defined f as a function/spline and then calculated r.
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| Feb 3, 2015 at 14:18 | comment | added | Peter Taylor | Then it's also unclear what the output format is. What should the arrow look like? How is the confidence interval communicated to your test framework? What counts as "getting it right" vs "getting it wrong"? And finally, I think that you should either replace "there might be ambiguous inputs" with a guarantee not to include any or say that in the case of ambiguous inputs any answer is wrong. Otherwise it's a guessing game, not a fair challenge. | |
| Feb 3, 2015 at 14:11 | comment | added | Peter Taylor | The basic task is unclear. I think that the two lines are meant to be the loci of two points which are separated by a constant amount (i.e. it's a "spherical cow in a vacuum" type of simulation), but surely that and the rather loose continuity constraint on one of them don't suffice to fully determine the evolution of the loci? An input could have both paths discontinuous and satisfy the stated constraints. I would like to see an explicit physical model or system of differential equations. | |
| Feb 3, 2015 at 10:43 | history | edited | flawr | CC BY-SA 3.0 |
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| Feb 2, 2015 at 21:41 | comment | added | flawr | 3. Both paths different colours, same (known) colours each time | |
| Feb 2, 2015 at 21:41 | comment | added | flawr | 2. Both paths different colours, colours arbitrary each time | |
| Feb 2, 2015 at 21:41 | comment | added | flawr | 1. Both paths black | |
| Feb 2, 2015 at 21:40 | history | answered | flawr | CC BY-SA 3.0 |