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Feel free to correct the grammar mistakes in my posts.


Apr
16
comment Dsolve is not solving equation ( 3 system with 2.order diferantial equations)
I think you're looking for @b.gatessucks right? :D
Apr
16
comment Dsolve is not solving equation ( 3 system with 2.order diferantial equations)
Well, so v9 can solve this set of equations? With v8.0.4, I only got the original input returned…
Apr
16
comment Solving System of Nonlinear with Three Differential Equations
Then you must have once mixed up = and ==. You need Clear[Derivative]. Values stored in Derivative can't be cleared by Clear["Global`*"] because it actually means clearing all the variables under context "Global`" while Context[Derivative] gives "System`".
Apr
16
comment Derive a PDE from other PDEs
You can refer to this post: mathematica.stackexchange.com/a/6428/1871
Apr
15
revised Compile with array operations
Add the forgotten description for the modification
Apr
15
revised Compile with array operations
Add the forgotten description for the modification
Apr
15
revised Compile with array operations
added 70 characters in body
Apr
15
answered Compile with array operations
Apr
15
comment Compile with array operations
Precisely speaking, I suggest you to at least avoid function definition based on pattern-matching. (see this post for details. )
Apr
15
comment ParallelTable, ParallelDo and ParallelMap all fail on simple evaluations, a BUG?
possible duplicate of Definitions inside ParallelTable?
Apr
15
comment ParallelTable, ParallelDo and ParallelMap all fail on simple evaluations, a BUG?
I think you need SetSharedVariable[Data].
Apr
15
comment Compile with array operations
Several observations: 1. qsum = MapThread[Plus, #] &@Rq can be changed to qsum=Total@Rq, 2. qsum = N[Plus @@ Fq] can be embedded into the definition of qf, 3. kr = ReplacePart[#, (\[Alpha] delta/Vf), 1] & /@ kr can be changed to kr[[All, 1]] = \[Alpha] delta/Vf. There still exists warnings but I'd like to stop here, as I mentioned above, I don't think compiling these code makes much sense.
Apr
15
comment Compile with array operations
Can you make some effort on reproducing your problem in a minimal code sample? BTW, I doubt even if you fix your code, it'll be slow since it has made so many external calls in Compile.
Apr
14
comment Plotting Fourier spectrum versus frequency of a signal
Your suggestion for changing sample size to 2048 and using a triangle does work (if I've understood it correct). Maybe you can consider improving your answer when you become more familiar with Mathematica, most people here are not familiar with signal processing after all :D
Apr
12
comment Solution To Nonlinear System
Or have I misunderstand your equations? Does those notations mean $\begin{array}{ll} \{ & \begin{array}{ll} (\text{r1}-\text{x1})^2+(\text{r2}-\text{x2})^2+(\text{r3}-\text{x3})^2==f \\ \text{r1} \text{z1}+\text{r2} \text{z2}+\text{r3} \text{z3}==\text{y1} \text{z1}+\text{y2} \text{z2}+\text{y3} \text{z3} \\ \frac{\text{r1} \text{v1}+\text{r2} \text{v2}+\text{r3} \text{v3}-\text{v1} \text{x1}-\text{v2} \text{x2}-\text{v3} \text{x3}}{\sqrt{(\text{r1}-\text{x1})^2+(\text{r2}-\text{x2})^2+(\text{r3}- \text{x3})^2}}==d \\ \end{array} \\ \end{array}$
Apr
12
comment Solution To Nonlinear System
Are you sure the solution can be found on the order of seconds? My Mathematica didn't give result for more than an hour, and I asked for a friend of mine using Maple for help and the equations ate up all the memory of his old machine.
Apr
12
comment Solution To Nonlinear System
And I'm afraid that the answer given by Mathematica will still be long and ugly due to the nature of the equations… How long has it taken matlab to solve these equations? I guess what really troubles you is the solution given by matlab "will divide by zero if the coordinate system is oriented a certain way", right? Perhaps you can elaborate it?
Apr
11
comment How should I use precision in this code?
Hello, welcome to mathematica.se! Then if you can make some efforts to reproduce your problem in a minimum example rather than paste all your code here and ask for debugging, I think your question will draw more attention and escape from downvotes. BTW, you don't need to paste your question for times, just edit it by clicking the "edit" button at the left bottom of your question.
Apr
11
comment Mathematica does not respect tensor order?
To be more precise, $Assumptions only works on functions with Assumptions option :)
Apr
11
reviewed Approve suggested edit on Generate array of every $n^{th}$ integer between two bounds