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)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <31212095.569.1367393879367.JavaMail.root@m06> <000001ce466b$56599700$030cc500$@comcast.net>

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 answer (mg98760) doesn't help much. Thanks in advance. 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}, > ContourShading -> False, > 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 >