Plotting an exponential exp(-x), in 3D?

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Ibrokhimbek Odinaev 2020-6-14

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https://ww2.mathworks.cn/matlabcentral/answers/548034-plotting-an-exponential-exp-x-in-3d

评论： Star Strider 2020-6-19

Hi, I want to plot exp(-x) which is e^-x, and revolve it around x=-5 in order to get a 3D solid that looks like a cooling tower of nuclear power plants. However the limit of y values should be from 1 to 200 which the height of the tower. How can I do that?

Thanks!

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Star Strider 2020-6-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/548034-plotting-an-exponential-exp-x-in-3d#answer_451065

在 MATLAB Online 中打开

Try this:

r = linspace(0.5, 5, 50);
a = linspace(0, 2*pi, 60);
[R,A] = ndgrid(r,a);
Z = exp(-R);
[X,Y,Z] = pol2cart(A,R,Z);
figure
mesh(X, Y, Z)
grid on

producing:

.Experiment to get it to look the way you want it to look.

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Star Strider 2020-6-18

在 MATLAB Online 中打开

I am not certain what you want.

This is the best I can do:

sval = 2.5;                                     % Shape Factor (Determines Vertical Curvature)
hval = 800;                                     % Height Factor (Determines Maximum Vertical Height)
inner_rad = 0.5;                                % Inner Radius (Top)
outer_rad = 1.1;                                % Outer Radius (Base)
r = linspace(inner_rad, outer_rad, 50);         % Define Radius (Vector)
a = linspace(0, 2*pi, 60);                      % Define Angle In Radians (Vector)
[R,A] = ndgrid(r,a);                            % Create Matrices For 3D Plot From Radius Vector & Angle Vector
Z = hval*exp(-R*sval);                          % Calculate Cooling Tower Shape (Matrix)
[X,Y,Z] = pol2cart(A,R,Z);                      % Convert Polar Matrices To Cartesian Matrices For 3D Plot
figure                                          % Create Figure Window
mesh(X, Y, Z)                                   % Create ‘mesh’ Plot Of 3D Cooling Tower
grid on                                         % Create Grid Lines On All Axes