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Sep
13
comment How do I plot x[t] vs. x'[t] (where x[t] and x'[t] are solutions to NDSolve)?
I just have edited (just) the formatting of your answer, because to me it looks like a very good solution to the question. One thing you might want to change is the naming of the variables which hold the solution, it usually is recommended to not use variable names which start with uppercase letters to stay out of conflicts with internal symbols.
Sep
13
revised How do I plot x[t] vs. x'[t] (where x[t] and x'[t] are solutions to NDSolve)?
just improved formatting a bit
Sep
13
comment Parallel computation of a system of differential equation
@GregoryRut: I see, that is of course a difference that I didn't have in mind: if you reinitialize you'll loose previous points, if you don't ProcessSolution will do the interpolation. I can't remember exactly but I think in older versions there was no way to get avoid the interpolation but in newer version it might be possible to extract results from StateData without building the full interpolation (or maybe it was just planned?) and continue without reinitialization. Anyway, fortunately there are also these other possibilities that I did mention...
Sep
12
revised Precision problem with numerical solution of a differential equation
added complete code example to problem as posted.
Sep
12
answered Precision problem with numerical solution of a differential equation
Sep
12
comment Parallel computation of a system of differential equation
@GregoryRut: Why do you think the answer given there was not a solution? I think it basically does what was asked for and also what you are intersted in: run NDSolve and only store the solutions at some points, you could of course also only store at one point, the end point. Neverthless you might find the additional answer that I just posted for that question also of interest, it gives a solution which is somewhat simpler if you really only are interested in the final value.
Sep
12
answered Only final result from NDSolve
Sep
11
comment Save output of NDSolve to a file
Have you seen this question?
Sep
10
answered Pick bug: level 0 matching
Sep
5
asked Known restrictions for WolframAlpha in CDF Player and PlayerPro
Jul
30
comment TimeConstrained for Table?
it probably would better to create an extra question for such a followup. But in this case I'm sure that you would create a duplicate as that has been answered before. You might search for SyntaxInformation. This should roughly do what you want: SyntaxInformation[TimeConstrainedTable] = {"LocalVariables" -> {"Table", {2, Infinity}},"ArgumentsPattern" -> {_, {_, _, _., _.} .., _}}
Jul
29
comment Mathematica9: NDSolve slows down after repeated calls
just tried it and it looks like the problem still exists in version 10
Jul
15
comment Controlling quality of discretized region meshes
good to see you back alive, user21 :-). Is it possible to refine the grid only near the edge, in one way or another?
Jul
6
comment Why are functions called first-class objects in Mathematica?
@Eric: one more remark about 3=9: for a term rewriting system this might not be that meaningless at all, e.g. it would work perfectly well in a local replace rule: (a+3) /. {3->9}. As far as I understand, the only reason why defining such a rule globally with Set wouldn't work is that Mathematica demands a global replace rule to be attached to a symbol, which in this case isn't possible as the LHS is just an atomic integer ...
Jul
6
comment Why are functions called first-class objects in Mathematica?
@Eric: as has been explained the "miracle" of Set is that it has the HoldFirst attribute. This will make Set see the unevaluated LHS. What the code within Set does with that unev. LHS is up to the programmers at WRI who wrote that code. Obviously it does analyze that LHS-expr. and for some special cases does "the right thing". There is nothing to be understood at the language level here, it really is just an implementation detail which even could change between versions. Unfortunately the documentation of what such functions actually implement is often somewhat vague or incomplete...
Jul
5
comment Why are functions called first-class objects in Mathematica?
I think the statement "{g,h,j}[[1]] = 6 can never work" is not correct. As Set has HoldFirst it would very well be able to extract the (held) symbol g and change its OwnValues, just as it is able to do in something like {g,h}={1,2}. Unlike the latter the former has not been implemented, probably for good reasons, probably just because nobody at WRI bothered about that specific case...
Jul
4
comment Why are functions called first-class objects in Mathematica?
I think that this statement might have had in mind "pure functions" like (#^2)& or Function[x,(1+x)^3]. These quite obviously are normal expressions and functions. "function definitions" like f[x_]:=... in Mathematica are actually definitions for global rewrite rules (as others have explained in more detail) which just happen to have an intuitive interpretation as functions but conceptually are not different from rules which e.g. define variable values.
Jun
8
awarded  Informed
May
28
answered Cell with no form using NotebookWrite
May
28
comment Cell with no form using NotebookWrite
yes, my porposal was that you explain in your answer what exactly it is that you refer to with "text cell". I guess you call a "text cell" one that has a string or TextData as content as opposed to an expression cell which has BoxData as content, which -- as you mentioned -- hasn't anything to do with its style, which can be "Text" or not. It probably also is worth mentioning that some functions (e.g. CellPrint and NotebookWrite) expect low level Cell expression as arguments while others (like CreateDocument) accept higher level stuff like TextCell...