# Better Accuracy for ContourPlot

Posted 10 years ago
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 Hi,Is it possible somehow to improve ContourPlot  accuracy?Here is the example when accuracy is not high enough.InvatiantJ = J + 0.13143284265648159 J^(3/2) Cos[3 \[Phi]];JDA = 25.728216396172527;InvatiantJDA = 8.576072132057504;Show[ ContourPlot[{InvatiantJ}, {\[Phi], 0, 2 Pi}, {J, 0, JDA},PerformanceGoal -> "Quality"], ContourPlot[{InvatiantJDA == InvatiantJ}, {\[Phi], 0, 2 Pi}, {J, 0,JDA}, PerformanceGoal -> "Quality"] ]All peaks for  the curve "InvatiantJDA == InvatiantJ" should be of the same heights, but they are not.I still can obtain a nice result with NSolve, but it's too slow.Off[Solve::ratnz];\[Phi]Tab = data = Table[2 Pi i/300, {i, 1, 300}];Do[data[[i]] = {\[Phi]Tab[[i]],    NSolve[InvatiantJDA == InvatiantJ /. \[Phi] -> \[Phi]Tab[[i]], J,      Reals][[1, 1, 2]]}, {i, 1, Length[\[Phi]Tab]}]ListPlot[data];Thanks,I.M.
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Posted 10 years ago
 Thanks, Ilian.
Posted 10 years ago
 Try increasing PlotPoints and MaxRecursion, for example Show[ContourPlot[{InvatiantJ}, {\[Phi], 0, 2 Pi}, {J, 0, JDA}, PerformanceGoal -> "Quality"], ContourPlot[{InvatiantJDA == InvatiantJ}, {\[Phi], 0, 2 Pi}, {J, 0, JDA}, PerformanceGoal -> "Quality", PlotPoints -> 100, MaxRecursion -> 2]]