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 >