wolfram-mathematica

问题 I'm searching for an algorithm to calculate the average distance between a point and a line segment in 3D. So given two points A(x1, y1, z1) and B(x2, y2, z2) that represent line segment AB, and a third point C(x3, y3, z3), what is the average distance between each point on AB to point C? I'm also interested in the average distance between two line segments. So given segment AB and CD, what is the average distance from each point on AB to the closest point on CD? I haven't had any luck with

问题 The sha1 hash of "abc" is a9993e364706816aba3e25717850c26c9cd0d89d The only way to get Mathematica to tell you that with its Hash function is Hash[abc, "SHA"] // IntegerString[#, 16]& (The IntegerString thing is just to output it in hex like most implementations do.) Note that Hash["abc", "SHA"] gives the hash of "\"abc\"" -- not what you want! In fact, the only reason we could get the correct hash of "abc" was because the Mathematica representation of the symbol abc happens to be the string

问题 I'm trying to get a Mathematica example working. It's the one on Theo Gray's blog. I think that Mathematica must have changed since he wrote that code (May 2008), since I'm unable to get anything reasonable out of it, despite changing nearly everything. Do I use ImageData instead of Import? Can anyone suggest a version of this code that works for Mathematica 8? imagePool = Map[With[{i = Import[#]}, {i, Mean[Flatten[N[i[[1, 1]]], 1]]}] &, FileNames["Pool/*.jpg"]]; closeMatch[c_] :=

问题 I'm trying to get a Mathematica example working. It's the one on Theo Gray's blog. I think that Mathematica must have changed since he wrote that code (May 2008), since I'm unable to get anything reasonable out of it, despite changing nearly everything. Do I use ImageData instead of Import? Can anyone suggest a version of this code that works for Mathematica 8? imagePool = Map[With[{i = Import[#]}, {i, Mean[Flatten[N[i[[1, 1]]], 1]]}] &, FileNames["Pool/*.jpg"]]; closeMatch[c_] :=

问题 I have data(points) that I have to import from another program to Mathematica, so I can plot it. I have control on how the points are going to be written to the file, so I can put them in any way I want. What is the best way to import them to Mathematica? As I'm going to use StreamDensityPlot, the variable I'll have to pass to StreamDensityPlot will have to be in the following way: data = { { { a, b, c }, {a, b, c}, {a, b, c}, { a, b, c }, {a, b, c}, {a, b, c}, { a, b, c }, {a, b, c}, {a, b,

问题 This is a strange result with a function defined as "functionB" in this example. Can someone explain this? I want to plot functionB[x] and functionB[Sqrt[x]] , they must be different, but this code shows that functionB[x] = functionB[Sqrt[x]] , which is impossible. model = 4/Sqrt[3] - a1/(x + b1) - a2/(x + b2)^2 - a3/(x + b3)^4; fit = {a1 -> 0.27, a2 -> 0.335, a3 -> -0.347, b1 -> 4.29, b2 -> 0.435, b3 -> 0.712}; functionB[x_] := model /. fit Show[ ParametricPlot[{x, functionB[x]}, {x, 0, 1}],

问题 I never worked too much with sounds in Mma. I have t = Sound[List["Violin",SoundNote[-6]]] How could I Export t as a .WAV file? When I try the obvious Export["c:\\test.wav",t] I get In this old thread Szabolcs said that it can't be done. Perhaps things have improved since 2007! 回答1: I think that it still can't be done. Mathematica supports creating and modifying MIDI objects, but leaves the sound generation from the midi to the underlying operating system. For now, you'll have to export to

问题 The output of the Mathematica command ListPointPlot3D[ Join @@ Table[{x, y, 0}, {x, -6, 6, 1}, {y, -6, 6, 1}], PlotStyle -> PointSize[0.02]] is the following image. I want to color the points (0,0) and (1,2) with the color red. How do I modify the above command for this? 回答1: A very simple and straightforward way would be: list = Join @@ Table[{x, y, 0}, {x, -6, 6, 1}, {y, -6, 6, 1}]; pts = {{0, 0, 0}, {1, 2, 0}}; ListPointPlot3D[{Complement[list, pts], pts}, PlotStyle -> PointSize[0.02]] Of

问题 Is there a way to combine the graphic of a ListPlot to the graphic of a Plot ? (I need to plot a graphic of a function on the graphic of a ListPlot) 回答1: You can combine any graphics with the Show function like so: Show[myListPlot, myPlot] This generalizes to combining any number of plots at once: Show[p1, p2, p3, p4, ...] or Show[{p1,p2,p3,p4,...}] Reference and image source: http://reference.wolfram.com/mathematica/ref/Show.html You can use Epilog as well if Show is not stacking the

问题 Evaluating the following integral should be non-zero, and mathematica correctly gives a non-zero result Integrate[ Cos[ (Pi * x)/2 ]^2 * Cos[ (3*Pi*x)/2 ]^2, {x, -1, 1}] However, attempting a more general integral: FullSimplify[ Integrate[Cos[(Pi x)/2]^2 Cos[((2 n + 1) Pi x)/2] Cos[((2 m + 1) Pi x)/2], {x, -1, 1}], Element[{m, n}, Integers]] yields zero, which is definitely not true for m = n = 1 I'd expect a conditional expression. Is it possible to "tell" mathematica about my constraints on