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Apr
7
comment String-manipulation bugs in v10.1
I also get same error , today 4/7/15, screen shot !Mathematica graphics
Apr
7
comment Animation of a geometric transformation
Could you please tell me what you get? the screen shot I pasted in the comment shows what I get. Clicking on it shows the output. I just copied and pasted your input, and the Plot I get, as you can see, is not the same as what you have. Windows 7, 64 bit, V 10.1
Apr
7
comment DSolve response with DSolve
Have you looked at the ODE themselves before passing them to DSolve? You can do this by splitting the cells, and evaluate the equations first to get an idea what is in them. Like this: !Mathematica graphics now one can see that the equations contain other derivatives of other dependent variables c2'[t],c4'[t],phi1'[t],phi3'[t],phi3'[t],phi4'[t]
Apr
7
comment Animation of a geometric transformation
fyi, the screen shot you show above (first one), is not what I get when I run your code under V10.1 !Mathematica graphics
Apr
7
comment What's the meaning of <<19>> in the result
this happens when you have large (long) output, and M shortens it. It is like etc....
Apr
6
comment NDSolve solving problem
You have second order ODE, but you only gave one IC. For numerical solver, it needs more one. (ps. the title of your question suggest it is a plotting problem, but there is no plotting issue here) (ps. actually the error message you get says the reason for the error :)
Apr
6
comment Solve ODE in State-space form
I do not know why the numerical gives these warnings, but your solutions are zero according to DSolve: w = 2; T = 2 Pi/w; a = 0.4; b = 4.0; d = 0.3; x[t_] := {x1[t], x2[t]} A0 = T {{0, 1}, {-a - b Cos[2 t], -d}}; sol = DSolve[{x'[t] == A0.x[t], x[0] == x'[0] == 0}, x[t], t] which gives {{x1[t] -> 0, x2[t] -> 0}} on V 10.1
Apr
6
comment How to stop Mathematica from turning .02 into 0.019999999999999997`
are you saying the correct valuate should be 0.02 exactly and M is not doing so? Could you post the source code to reproduce? hard to see the image, too small and need magnifying glasses to see.
Apr
5
comment Is association in mathematica ordered or not?
I have not used association much, but for me, it makes little sense to talk about "order" of keys. The point is that one gives a key, and gets the value associated with that key by a lookup. Like a hash table. If you depend on an "order" of keys in the lookup table to do something, then I think you are doing something wrong.
Apr
5
comment How to draw block diagrams as Graph objects?
These can also be made with latex/tikz
Apr
4
comment Draw and Quantity
@AlbertRetey good point. Since the units are all the same in this example, this will not make a difference, but will update for illustration and to remind one of this. thanks.
Apr
4
comment Draw and Quantity
@Luca M is not OO Language, but uses functions. So to find what "methods" can be used on "object" Point you look at help and see all the settings and commands that can be applied to it. Also if you do ??Point you'll see the options Options[Point]={VertexColors->None,VertexNormals->None} There are also modifiers you can apply to point, such as PointSize and change its color etc...
Apr
3
comment How can I create a phase plane?
You should not be using UpperCase letters really, but if you must, use a numbered ones, like N0, C0, etc... in addition, N and C are mathematica own symbols so using them for variables will get you in trouble very quickly.
Apr
3
comment How can I create a phase plane?
there are number of posts on this topic. For example mathematica.stackexchange.com/questions/14160/… and others.
Apr
3
comment Rewriting symbol context?
fyi, added an example how to extract the symbols from the replacement list automatically so no need to write them down.
Apr
3
comment Rewriting symbol context?
I do not get it. You had to type the long replacement rule of 50 replacements? So why not type one variable that is a list of all the symbols? Like this: paramList = {y -> 1, z -> 2} mySymbols = {x, y, z}; sol = f[mySymbols, paramList] You only have to type the list once and then use it. This is for me the clean solution, other than making a wrong API, then try to figure what hacks to do to fix things afterwords. But this is just how I would do it. If you wait more, may be you'll have better suggestions how to handle this. good luck.
Apr
3
comment What are the cool kids talking about when they use ##&[]?
@raxacoricofallapatorius you can also write If[# == 1, Sequence @@ {}, #] & /@ {1, 2, 3} which gives {2, 3} also. but from now on, I will use ##&[] to be more cool.
Apr
3
comment Rewriting symbol context?
fyi, updated my answer with your example of how I would do it to avoid the context mix problem.
Apr
3
comment Rewriting symbol context?
The example you showed shows exactly the problem I was talking about below. You can't mix symbols from different contexts. The way you are implementing this is not correct. The y and z in your example are in package context while the y and z you are passing are from global context. I suggest writing this as I showed below, otherwise, you'll have to do hacks and other such things to fix things. So better do things right from the start (my 2 cents ofcourse)
Apr
2
comment What are the cool kids talking about when they use ##&[]?
So the bottom line is that all these 3 do the same thing: Map[If[# == 1, Unevaluated@Sequence[], #] &, {1, 2, 3}]; If[# == 1, Unevaluated@Sequence[], #] & /@ {1, 2, 3}; If[# == 1, ## &[], #] & /@ {1, 2, 3}; so use the last one above. It is not only shorter than all the others, but also makes you look much smarter as well.