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plotting - ContourPlot with certain contour values omitted


Suppose I want contour plot of x2−y2, for x,y\in[0,1] (my actual function is more complicated). Over this interval, x^2-y^2 is sometimes positive and sometimes negative. Using ContourPlot I get all the contours, negative as well as positive.


But what if I wanted only those contours with values \geq 0 to show, while those contours whose value is less than zero are not displayed or (worst case) shown by the same color (say white). I doubt if this is possible at all, but any help is much appreciated.



Answer



You can use the option RegionFunction:


ContourPlot[x^2 - y^2, {x, 0, 1}, {y, 0, 1}, RegionFunction -> (#^2 >= #2^2 &)]


enter image description here


Or use ConditionalExpression


ContourPlot[ConditionalExpression[x^2 - y^2, x^2 >= y^2], {x, 0, 1}, {y, 0, 1}, 
 Contours -> 4]

enter image description here


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