MATLAB: How can i represent 2 functions on the same graph

functionfunctionsgraphMATLABplotplotting

I am having an issue in representing two functions in one graph as i cant solve them in order to the same variable ( x or y. The two functions are: 2x^3-5x-2y^3+1=0 and x^4+4y^4y-6=0

I have tried using plot, mesh , hold on etc but nothing seems to work… Does anyone have an ideia ?

Best Answer

One option is the fimplicit (link) function:

f1 = @(x,y) 2*x.^3-5*x-2*y.^3+1;
f2 = @(x,y) x.^4+4*y.^4.*y-6;
figure(1)
fimplicit(f1, [-10 10 -10 10])
hold on
fimplicit(f2, [-10 10 -10 10])
hold off
legend('f_1(x,y)', 'f_2(x,y)', 'Location','NW')

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 fimplicit(@(x,y) x.^2 + 4*x.*y +5*y.^2 - 10,'r'); hold on; fcontour(@(x,y) 3*x+4*y) ; hold off

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Here is one approach:

f = @(x,y) x.*y.*(x.^2+y.^2) - 47.3;
figure
fih = fimplicit(f, [-10 10  -10 10]);
xv = fih.XData;
yv = fih.YData;
v0 = ones(size(xv));
Lpos = xv>=0;
xpos = xv(Lpos);
ypos = yv(Lpos);
xneg = xv(~Lpos);
yneg = yv(~Lpos);
xneg = xneg(~isnan(xneg));
yneg = yneg(~isnan(xneg));
hold on
% fimplicit(f2, [-10 10  -10 10])
yl = ylim;
xl = xlim;
patch([xpos fliplr(xpos)], [ones(size(ypos))*max(yl) fliplr(ypos) ], 'r')
patch([fliplr(xneg) xneg], [ones(size(yneg))*min(yl) (yneg) ], 'r')
hold off
grid

This is not a straightforward problem, so it could be difficult, especially since the NaN values could be difficult to find and elimiinate, and they are not obvious.

The filled areas are those that conform to the stated inequality.

I evaluated them from -10 to 10 with respect to both variables. Change those to get different results.

Best Answer

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