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| bio | website | uoregon.edu/~noeckel |
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| location | ||
| age | ||
| visits | member for | 1 year, 3 months |
| seen | 7 mins ago | |
| stats | profile views | 1,324 |
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May 22 |
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Exporting a dashed plot with a color gradient to a vector graphics format ruins the dashing The answer given by @Peter below is based on a post by me on MathGroup. I also gave it as an answer on this web site, see the bottom of my answer. |
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May 21 |
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How to define a non-standard algebra in Mathematica? A related discussion of custom notation for an operator algebra: Having the derivative be an operator |
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May 21 |
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Automatically check student answers in tests @R.M. I agree - at the moment my white-list consists of symbols, and of functions that have attribute NumericFunction. If it turns out I should be more restrictive, I'll do that. I think that the current filter is enough to prevent ToExpression to be exploited for injecting code because NumericFunction functions aren't able to do that. If I'm wrong about that, I'd certainly be able to just admit just the "scientific calculator" range of functions. |
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May 19 |
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How can locators be added to the points on a 3D grid? Looks like the code came from szabolcs on Mathgroup. |
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May 19 |
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Automatically check student answers in tests I think my conclusion is that it may really be better to use a "dumber" approach - an interface where symbolic manipulations are inaccessible. That's what the AcroTeX bundle does, which I mentioned in my comment to the question. I.e., use numerical checks even when the input is a free-form function and not a number. |
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May 19 |
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Automatically check student answers in tests But it never seems to end: what about the following: ToExpression[StringReplace["integrate[2 z^2,z]","i"->"I"]] |
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May 19 |
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Automatically check student answers in tests Oh yes. That's what happens when I try not to find cheats and stay honest... |
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May 19 |
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Automatically check student answers in tests The current version doesn't work at all. I enter 2/3x^3 and it returns WRONG. |
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May 19 |
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NDSolve and results of the previous computations First of all, you can already solve for R(t) by hand. Second, the remaining equation probably should have C replaced by C_i. Is that what you mean? You will then also need the initial conditions for all C_i, I would guess. With that, you would have a coupled system of first-order equations in time for the C_i. |
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May 19 |
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Automatically check student answers in tests Referring to the example CDF at the link posted by Vitaliy: it needs a lot more thought. The particular question can easily be tricked if you know that the indefinite integral can also be written as f[z_] := 2 z^2; Derivative[-1][f][z]. Enter this, and it says you're correct. So for this particular type of testing, which I agree is an important subject, the proposed approach is still not an acceptable solution. |
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May 18 |
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Automatically check student answers in tests @Gabel Yes: it fails because the input field functionality required for this suggestion is not supported by the free CDF format. That detail was indirectly hinted at in some general language about CDF in point 2) above. For now, I would strongly suggest taking a look at the example files for AcroTeX, e.g., the "Multivariate Questions" |
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May 18 |
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Automatically check student answers in tests I still don't see a practical answer here, compared to what AcroTeX has been able to do for years. I'll try and look into that bundle again and see if it can be realized in MMA. Maybe you'll make your answer workable in the meantime... |
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May 18 |
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Automatically check student answers in tests @Andrew The question asks for something where the students enter their answers and get feedback. I'm simply pointing out that the main issue of the question isn't addressed in this answer - so I personally would not have posted that. |
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May 18 |
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Automatically check student answers in tests This cannot work because the student could simply enter the following input: Integrate[2 z^2,z]
and get full credit. |
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May 18 |
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Automatically check student answers in tests There is also the AcroTeX eDucation Bundle which I have used a few years ago, and just checked that it still is freely available. When I used it, I was impressed how it can take free-form input of functions and checks them for correctness - purely with JavaScript in a PDF document displayed with Adobe Reader. The trick they used to check functions is not to try and symbolically simplify them, but to numerically compare them to the correct solution at certain x-values. |
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May 18 |
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How to define and work with temporary graphics data? @Szabolcs Do you think this $iterationLimit/2 limit should be reported as a bug? |
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May 18 |
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What does DisplayFunction->Identity do to graphics functions? @Szabolcs Good point - I don't have any specific use in mind right now anyway... |
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May 18 |
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Borked Find Window in OS X When this happens, do you have Dynamic enabled and is a dynamic cell visible somewhere else in the notebook? I've never seen this - is it possible to click on the Plus sign at the top right of that dialog to see the error message? |
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May 18 |
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Start Mathematica without the menu bar? That's true - it has a clunky feel to it... |
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May 17 |
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What does DisplayFunction->Identity do to graphics functions? This could be very useful for defining wrapper functions globally as in SetOptions[Plot, DisplayFunction-> myFunctiom]. |
