Trying to plot two equations with ezplot.

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Nick Barker 2015-7-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230826-trying-to-plot-two-equations-with-ezplot

评论： Star Strider 2015-7-22

Hello:

I am trying to plot a pair of simultaneous equations to see at which points they intersect for a given interval 0 to 6pi. The first equation would be plotted in green and the second equation would be plotted in blue.

My code is as follows:

c=input('c');
syms p q 
eqn1 =(p^2*q^2*(q^2+p^2)+c^2*(p^4+q^4-6*p^2*q^2)-3*c^4*(p^2-q^2)-4*c^6)*sin(p)*sinh(q)+2*p*q*(-p^2*q^2+3*c^2*(p^2-q^2)-7*c^4)*cos(p)*cosh(q)-p*q*(p^4+q^4+2*c^2*(q^2-p^2)+2*c^4)*cos(2*c)==0;
eqn2 = 2*c*p*(3*p^2*q^2-q^4-c^2*(p^2+q^2)+4*c^4)*cos(p)*sinh(q)+2*c*q*(p^4-3*q^2*p^2-c^2*(p^2+q^2)-4*c^2)*sin(p)*cosh(q)+p*q*((p^2+q^2)*(q^2-p^2+2*c^2))*sin(2*c)==0; 
a = axes;
h = ezplot(eqn1);
h.LineColor = 'green';
hold on
grid on
g = ezplot(eqn2);
g.LineColor = 'blue';
L=sym(0:pi:6*pi);
a.PTick = double(L);
a.QTick = double(L);
M = arrayfun(@char, L, 'UniformOutput', false);
a.PTick = M;
a.QTick = M;
title('Plot of System of Nonlinear Equations')
legend('eqn1','eqn2', 'location', 'best')  
% code

However, when I run the script, both of my equations come out in the same color: green. For example, when I choose for my input of c to be 1, my plot comes like this: