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 Jul 8 comment Rotating an image along a Möbius strip? @Mr.Wizard Sorry, I haven't used this package since this answer ... I don't know. Jul 8 comment Generate Random 3D Network using GraphPlot3D and loop "does it really matter?" <-- Well, that depends on what you want to do with the network and it's up to you to decide. If you want to use it for research, then yes, it matters a lot, as the type of random graph model you use will influence the results you get. In Mathematica, RandomGraph[{n,k}] ensures uniform distribution. Jul 7 comment Can I use symbolic tensors for simple linear algebra and calculus? I think calculus functions (D) don't work with tensors. D seems to work with Dot, but it does give a weird looking result that I don't understand: 1 . x (anyone copying this, note the space around the .). This type of expression will never evaluate 1 . 2 or 1 . {1,2}. I would have expected Dot to act as Times with scalars ... Jul 6 revised How to draw a combinatorial graph with different colors of edges? added 156 characters in body Jul 6 comment Coupled ODEs with boundary conditions - DSolve Error To clarify acl's comment, after clearing these symbols (or restarting the kernel), DSolve will not give any errors, but it will still not be able to solve the system. You can use NDSolve to get a numerical solution when getting an analytic solution is not possible. Jul 6 answered How to draw a combinatorial graph with different colors of edges? Jul 6 comment Make AdjacencyGraph hide single unconnected elements If you don't want to remove them, there's probably a way to hide them through VertexShape and EdgeShape, but this is likely going to be more difficult and the way the graph is drawn will still be affected. Jul 6 answered Make AdjacencyGraph hide single unconnected elements Jul 6 comment How can I avoid a scoping problem when differentiating? Derivative[1, 0, 0][hh][x, y, i] is equivalent to D[hh[x, y, i], x], but now you don't have to write x explicitly, so it avoids the problem. Jul 5 comment 256 Shades of Grey @DumpsterDoofus Natural dithering is why this problem never comes up with photos. But I do sometimes see clearly visible posterization in OpenGL-rendered stuff (not dithered). Jul 5 comment Is there a Real equivalent to FromDigits? @kguler Post an answer? It seems it's worth spelling out because people are not always aware that FromDigit already does this. Jul 5 comment 256 Shades of Grey As @m_goldberg says, usually 256 shades are enough, as the screen (!) and eye can't distinguish more. But it can indeed happen on some screens that it's possible to see the posterization effect with only 256 shades and no dithering. I can sometimes see this on my screen, and if I look very very carefully at your image and keep moving the screen (or my head) left and right, then I can (barely) see posterization in your image too. But just barely. There must be some processing in the human eye that accentuates the difference when I move the screen, but not otherwise. Jul 5 comment 256 Shades of Grey @DumpsterDoofus You can represent more than 256 shades of grey. In fact by default Image uses floating point values for pixels which can represent a very large number of shades (see ImageType). However, Mathematica cannot display more than 256 shades of grey. (Certain programs on certain operating system can display 1024=2^10 shades if the hardware supports it---that means video card and screen, I think.) So the question: is your aim to represent more than 256 shades, or to display them? The first is easy, the second can be approximated by dithering. Jul 4 comment Liouville theorem demonstration I've given you a starting point. If you are looking for a complete solution, people are unlikely to put in the effort to write one, unless you demonstrate that you put in the effort to learn a bit of Mathematica and at least try to solve the problem. Jul 4 answered Liouville theorem demonstration Jul 4 comment Create a colorbar plot legend @dimitris Check the predefined colour palettes (look up ColorData and Color Schemes in the palettes menu), or you can build your own using Blend. Jul 4 comment Datastream to Mathematica I don't understand completely what you are trying to do. How does Excel come into the picture? And can you include some links to this datasource or some documentation decribing the API that allows accessing it? What sort of API is it? Jul 4 revised Datastream to Mathematica deleted 36 characters in body Jul 4 comment Create a colorbar plot legend @bobthechemist Yes, I did! Jul 4 revised Create a colorbar plot legend edited body