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MathGroup Archive 2004

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Re: converting table output and plotting

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49126] Re: converting table output and plotting
  • From: "seferiad" <seferiad at pacbell.net>
  • Date: Fri, 2 Jul 2004 02:01:28 -0400 (EDT)
  • References: <cbu2kr$5i6$1@smc.vnet.net> <cc0n4j$l0f$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Paul,
Works great. Thanks (oops about the Solve).

When I try to utilize a single equation with v and i, with no intermediate
i1, I find that Mathematica has trouble. I don't understand this.

Thanks,
Jay


"Paul Abbott" <paul at physics.uwa.edu.au> wrote in message
news:cc0n4j$l0f$1 at smc.vnet.net...
> In article <cbu2kr$5i6$1 at smc.vnet.net>,
>  "seferiad" <seferiad at pacbell.net> wrote:
>
> > Hello,
> > I have the following equation:
> >
> > Table[{v, NSolve[{i == v/r2 + i1, i1==i1(r1+r2)/r2  + a/r2*Log[i1/io +
> > 1] - v/r2} /. {r2 -> 200, r1 -> .025, io -> 10^-9, a -> .05}, {i,
> > i1}]},{v, 1, 1.2, .1}]//ColumnForm
> >
> >
> > OUTPUT IS:
> >
> > {1, {{i->.402, i1->.397}}}
> > {1.1{{i->1.611,i1->1.60}}}
> > {1.2,{{i->3.86, i1->3.85}}}
> >
> >
> > The first terms 1, 1.1,1.2 are Voltage (v) and the second term is
> > Current (i), the third term is Current1 (i1).
> >
> > My objective is to vary my equation above and then create the output
> > in such a form that I can directly plot v vs. i, that is "1st term"
> > vs. "2nd term".  Unfortunately, I don't know how to do this since the
> > outputs in the table aren't as I like.
> >
> > Note: My original approach was to write the transcendental equation in
> > a single form whereby, NSolve[ i == function (v, i) ]  Unfortunately,
> > Mathematica seems to choke on this one.  By calculating an additional
> > (uninteresting) value (namely, v1), it gives me the output I'm looking
> > for. Again, except that I don't know how to convert this into a set of
> > numbers that I can plot.
>
> Your set of equations can be solved exactly for i and i1:
>
>   solution =
>   Solve[{i == v/r2+i1, i1==i1(r1+r2)/r2+a/r2 Log[i1/io+1]-v/r2},{i, i1}]
>
> A table of numerical values agrees with those obtained using NSolve:
>
>   parameters = {r2 -> 200, r1 -> 0.025, io -> 10^(-9), a -> 0.05};
>
>   Table[{v, solution /. parameters}, {v, 1, 1.2, 0.1}]
>
> You can plot the solution v versus i as follows:
>
>   ParametricPlot[Evaluate[{i, v} /. solution /. parameters], {v, 1, 2},
>    AxesLabel -> {i, v}]
>
> (You could just use Plot to visualize i versus v).
>
> Cheers,
> Paul
>
> --
> Paul Abbott                                   Phone: +61 8 9380 2734
> School of Physics, M013                         Fax: +61 8 9380 1014
> The University of Western Australia      (CRICOS Provider No 00126G)
> 35 Stirling Highway
> Crawley WA 6009                      mailto:paul at physics.uwa.edu.au
> AUSTRALIA                            http://physics.uwa.edu.au/~paul
>


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