How can I make the z axis smaller in order for the absolute maximum and absolute minimum to show up on my graph? How can I plot the absolute max/min points in contrasting size and color?

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Alejandro Avelar 2019-4-23

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评论： Walter Roberson 2019-4-23

So, I have my code, but I am confused on how I can change the z axis to show all 5 of my points. the absolute maximum is 40 at (2,2) and the absolute minimum is -0.125 at (-1/2,0) and (1/2,0).

% Code Plane and Boundaries
x=linspace(-5,6,50); 
y=x;
[X,Y]=meshgrid(x,y);
 
Z=2.*X^4-X.^2+3.*Y^2;
surfl(X,Y,Z)
grid on
hold on
 
x1=linspace(0,16,30);
y1=linspace(0,0,30);
z1=2.*x1.^4-x1.^2;
 
plot3(x1,y1,z1,'r*','Markersize',15)
hold on
 
x2=y1; 
y2=x1; 
z2=28+3.*y2.^2;
 
plot3(x2,y2,z2,'r*','Markersize',15)
hold on
 
x3=x1; 
y3=x3; 
z3=2.*x3.^4-x3.^2+3.*y3.^2;
 
plot3(x3,y3,z3,'r*','Markersize',15)
hold on
 
crx=[-1/2, 1/2,0, 2, 2];
cry=[0, 0, 0, 0, 2];
crz=2.*crx.^4-crx.^2+3.*cry.^2;
plot3(crx,cry,crz,'bd','Markersize', 15,'Markerfacecolor','b')
hold off

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Answer 1

Walter Roberson 2019-4-23

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在 MATLAB Online 中打开

All 5 markers are plotted. The difficulty you are having is that on that scale, the 3rd marker is so close to the first marker that it is difficult to notice the difference between them, especially as the pane runs right through the third marker

You can use, for example,

zlim([-5 45])

You might want to also use xlim() and ylim() calls.

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Alejandro Avelar 2019-4-23

Thank you very much. Is there any way in which the max and min points can be edited to look bigger than the rest of the points?

Walter Roberson 2019-4-23

You might want to use scatter3() to draw the markers instead of plot3(). When you use scatter3() then you can specify a different marker size for every marker.

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