PatrickT

Dr. Patrick T

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13 years, 96 days

MaplePrimes Activity


These are answers submitted by PatrickT

For future reference let me consign here a useful piece of info for the use of the dsolve option  "events" in conjunction with "halt".

One can retrieve the time of the trigger with the following:

 rhs(SOL[1](last)):

where SOL[1] extracts the "time" range and "last" extracts the last evaluation thereof:

SOL := dsolve([SYS,INI], VAR, type = numeric, etc.
    [t = proc(t)  ...  end;, u(t) = proc(t)  ...  end;, etc

as it happens, I came across this very useful document on how to deal with stiff ODE, in addition to the Maple help files, could be useful to you.

http://www.cbu.edu/~wschrein/media/ANA/stiff.pdf

I support Duncan's suggestion of exporting as pdf. I personally use the freeware cutepdf. After it's installed (windows), you can select print and then cutepdf from any application, not just maple but word processors, image viewers, etc.

It could be a stiff problem, it could be that you need to tweak the degree of precision, the range, etc. Please copy-paste your code or a minimal example. If you upload your worksheet instead, the response rate will be significantly lower, as it is time consuming to download and open a worksheet.

there are many parameters that determine the quality of a printout, so it's difficult to comment on your particular situation.

you say you have produced jpg figures that look good on screen but don't print well? is that the case with other jpg figures not produced from Maple?

Is there a difference between printing the figures from within word and outside of word? maybe word compresses your figures when you import them within?

I personally output postscript or pdf figures and use LaTeX to write my stuff.

Maple does not handle (at least not directly) this sort of condition. Perhaps you can solve the two cases separately such that the boundary conditions of sys2 take the end-values of sys1 as start-values (or vice versa),

sys1:=[diff(c(x,t),t)=v(x,t)*diff(c(x,t),x$2),diff(v(x,t),t)=c(x,t)*diff(v(x,t),x$2)];
sys2:=[diff(c(x,t),t)=v(x,t)*diff(c(x,t),x$2),diff(v(x,t),t)=0];

you'd be more likely to get help if you copy-pasted your code, as it is sometimes tedious to open a worksheet.

You've got something like this:

Foco:

Foco1:

you're using the same method, rkf45 to solve both. One difference I can see is in maxfun. Have you tried to play around with maxfun? Have you tried using different solution methods other than rkf45?

always a simple place to start if you're stuck: plot the expressions and examine the graph, as you let 1 or 2 parameter values vary within the admissible range.

Note that, if I'm reading correctly, F1(S)>0, so you just need to analyze R*S*G = R*S*R3*k*(1-R1)/(C*Peci), and check whether/when it's above/below the value 1.

Have you followed the authors' instructions? in the readme file it says:

To install the package simply add the full path of directory lib in the variable libname
in MAPLE initilazation file (.mapleinit in LINUX) or simply put the file inside directory lib
in the MAPLE main lib directory.

There are 2 files inside the "lib" directory, SADE.ind and SADE.lib, I copied them into Maple's own "lib" directory (under Program Files, etc) and tested the example named solving_ODE.mw, it ran and solved the example. No error message. Can you try this and report back if you're having problems?

just occurred to me, this may be what you were looking for:

plottools:-reflect(plottools:-rotate(p,Pi/2),[[0,0],[0,1]]);

P.S. I came upon this thread by googling for "maple exchange x and y axis" and was quite shocked to see that I once knew something about the topic. However, on second thoughts, the above is more likely to be useful than my first suggestions.

If I understand correctly, you also want to know how many days it will take to reach the lake, 5 miles away. About 83 days for Tom:

evalf( solve( sum(1/k,k=1..n) = 5, n ) );
                          82.82747564

Note the use of "sum" instead of "add" here.

But Jerry doesn't make it: 4 miles is as far as he'll get poor snail.

ptom := plots:-pointplot([seq([n,tom(n)], n=1..100)], color=red):
pjer := plots:-pointplot([seq([n,jerry(n)], n=1..100)], color=blue):
plots:-display(ptom,pjer);

not sure what you're looking for, this C*exp(-k*x) is the solution of an ODE? perhaps what you're asking is how to solve an ODE with boundary conditions?

can you copy paste the part of the code you're talking about?

Robert, I'm very grateful for your help. I've got a few more questions if that's okay.

What would be the general formula for the (N!) x (N!) matrix Q ? Is there a way to generate it with Maple's Matrix constructor?

 

Background note: What I'm trying to do is to replicate a particular race involving about 8 cars. I'd calibrate (somehow, probably very roughly) the probabilities based on actual data. Since I'd use actual numbers, I'm hoping Maple would be able to handle such a huge matrix.

you can do something like this:

plotsetup(ps,plotoutput=`myFigure.ps`,plotoptions=`axiswidth=400pt,axisheight=300pt`)

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