Re: Getting Coordinates from plot

• To: mathgroup at smc.vnet.net
• Subject: [mg32967] Re: [mg32953] Getting Coordinates from plot
• From: BobHanlon at aol.com
• Date: Fri, 22 Feb 2002 01:48:50 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```In a message dated 2/21/02 4:04:10 AM, uceswga at ucl.ac.uk writes:

>I would like a list of coordinates so that I can analyze them further
>and possibly import into a "prettier" graphing package. What should
>I do when using the NDSolve function?
>
>I have tried the menu command: Input -> Get Graphics Coordinates.
>This requires me to use Mod1 key which I don't have on my keyboard.
>
>How can I get coordinates of the plot from the following:
>
>
>Pends[init1_, init2_, time_, k_, {c_, w_, p_}] :=
>      Module[{},
>        pend = NDSolve[{
>     x1''[t] + c x1'[t] + ((1 + p Cos[w t])) Sin[x1[t]] == k (x2[t] - x1[t]),
>
>          x2''[t] + c x2'[t] + ((1 + p Cos[w t])) Sin[x2[t]] == k (x1[t]
>- x2[t]),
>              x1[0] == init1[[1]], x1'[0] == init1[[2]],
>              x2[0] == init2[[1]], x2'[0] == init2[[2]]},
>         {x1, x2}, {t, 0, time},
>         MaxSteps -> 200000];
>         xd[t_] := x1[t] /. pend[[1]];
>         xdd[t_] :=x1'[t] /.pend[[1]];
>         xr[t_] := x2[t] /. pend[[1]];
>         xrd[t_] :=x2'[t] /.pend[[1]];
>         ];
>   c = 0.1;  w = 2.0;  p = 2.0;
>   Pends[{1.37, 0}, {-1.17, 0}, 5000, 0.0, {c, w, p}];
>   ParametricPlot[{ {xd[t], xdd[t]}, {xr[t], xrd[t]}}, {t, 1000, 1500}];
>

plt = ParametricPlot[{ {xd[t], xdd[t]}, {xr[t], xrd[t]}}, {t, 1000, 1500}];

The data for the first plot is plt[[1, 1, 1, 1, 1]]

The second plot is plt[[1, 2, 1, 1, 1]]

To compare with the original plot

Needs["Graphics`Graphics`"];
DisplayTogether[
ListPlot[plt[[1, 1, 1, 1, 1]], PlotJoined -> True],
ListPlot[plt[[1, 2, 1, 1, 1]], PlotJoined -> True]];

Bob Hanlon
Chantilly, VA  USA

```

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