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Re: export differential equation solution obtained through Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106338] Re: export differential equation solution obtained through Mathematica
  • From: dh <dh at metrohm.com>
  • Date: Fri, 8 Jan 2010 06:28:45 -0500 (EST)
  • References: <hi6t6f$a6k$1@smc.vnet.net>


Hi,

obviously the output of NDSolve is a numerical function not an 

anayltical one. Therefore, the best you can do is to create a table with 

  p and t values. This data you may the export e.g. to a CSV (or other 

formated), file that can be read by EXCEL.

Here is an example:



sol = f /. NDSolve[{f' [t] == f[t], f[0] == 1}, f, {t, 0, 1}][[1]]

dat = Table[{t, sol[t]}, {t, 0, 1, .1}]

Export["d:/tmp/t.dat", dat, "CSV"]



Daniel



Yun Zhao wrote:

> Hi everyone,

> 

>   I would like to know if there is a way to export differential equation

> solution obtained through Mathematica to microsoft excel.  There are several

> data processing things that I want to know, that simply plotting the

> solution in Mathematica won't suffice.

> 

>   I have a system of differential equations like so:

> 

> 

> sol3=NDSolve[{p'[t]=-0.0491*p[t]-0.0089*p[t],n'[t]=0.0491*p[t]+(0.0491-0.0089)*n[t],p[0]=25000,n[0]=0},{p,n},{t,0,100}]

> 

> When I plotted it in Mathematica using this code:

> 

> Plot[Evaluate[{n[t]+p[t]}/.First[sol3]],{t,0,100}]

> 

> I get a exponential increasing function plotting number vs. time.

> 

> What I want is the values of both the time vector and number vector, and I

> want to copy and paste them into two columns in microsoft excel.

> 

> I tried using:

> 

> Export["newdata.dat", Evaluate[{n[t]+p[t]}/.First[sol3]]

> 

> But this gives me a .dat file with the time and number vectors all scrambled

> up.

> 

> My question is:

> 

> (1) is there a better way to tell Mathematica what I want to export, because

> I don't think Evaluate[{n[t]+p[t]}/.First[sol3] is the correct term to

> convey what I want

> 

> (2) How do I properly export differential equation solutions that I can

> graph but not display in Mathematica, to spreadsheets software like

> Microsoft Excel?

> 

> 

> 

> Thank you all very much.

> 

> 




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