       Re: Intersection points of two contour plots

• To: mathgroup at smc.vnet.net
• Subject: [mg130683] Re: Intersection points of two contour plots
• From: Luiz Melo <lmelo at ufsj.edu.br>
• Date: Wed, 1 May 2013 21:41:51 -0400 (EDT)
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```Hi,
The given example was just to illustrate. In the original problem, I
cannot specify the region function. Also,
I have two tables t1 and t2 with a finite number of points, and I use
ListContourPlot with the option Contours -> {0} to see the contours at
z = 0. The solution to my problem occurs when both t1 and t2 intercept
at z = 0, as in the example given.

I can reformulate my problem in the following way: Given some contour plot

p0 = ListContourPlot[Table[Sin[3 x*y], {x, -3, 3, .1}, {y, -3, 3,
.1}], Contours -> {0}, ContourShading -> False,
DataRange -> {{-3, 3}, {-3, 3}}, ContourStyle -> Black];

How to extract the x and y coordinates of the plot p0 in the form of a
list of values t0 = {{x1,y2},{x2,y2},....} . ??
I found an old thread (mg98726) involving the same issue, but the

Luiz

On Wed, May 1, 2013 at 9:56 AM, djmpark <djmpark at comcast.net> wrote:
> Do you want something like this:
>
> ContourPlot[Sin[3 x y], {x, -3, 3}, {y, -3, 3},
>  Contours -> {0},
>  ContourStyle -> Red,
>  RegionFunction -> Function[{x, y}, x y <= 0],
>  Exclusions -> {x == 0, y == 0}]
>
>
> David Park
> djmpark at comcast.net
> http://home.comcast.net/~djmpark/index.html
>
>
> From: Luiz Melo [mailto:lmelo at ufsj.edu.br]
>
>
> Hi group,
> Please consider the example below to illustrate my question (the original
> problem is somehow much more complicated):
>
> t1 = Table[Sin[3 x*y], {x, -3, 3, .1}, {y, -3, 3, .1}];
>
> t2 = Table[If[x*y < 0, Sin[3 x*y]], {x, -3, 3, .1}, {y, -3, 3, .1}];
>
> p1 = ListContourPlot[t1, Contours -> {0}, ContourShading -> False,
>    DataRange -> {{-3, 3}, {-3, 3}}, ContourStyle -> Black];
>
> p2 = ListContourPlot[t2, Contours -> {0}, ContourShading -> False,
>    DataRange -> {{-3, 3}, {-3, 3}}, ContourStyle -> {Red, Dashed, Thick}];
>
> Show[p1, p2]
>
> Is there a way to show only the results of the intersection of these two
> contour plots?
>
> Thank you
> Luiz
>

```

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