how do I plot 3d graph?

Question

donghun lee 2020-4-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/515493-how-do-i-plot-3d-graph

评论： Ameer Hamza 2020-4-5

clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
fig = figure();
ax = axes();
hold(ax); 
% view([-53 33]);
grid on
l_array = linspace(0.1,1,100); %Excitation Amplitude
d_array = linspace(-0.1,-1,100);
T = 150;
x0 = [0,0];
xval = zeros([],1) ; 
yval = zeros([],1) ; 
for i=1:numel(l_array)
    for i=1:numel(d_array)
    l = l_array(i);
    d = d_array(i);
    k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
    
f = @(t,x) [ x(2); ...
    -(2*k_s*(x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))* ...
    (sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2) - l))/ ...
    (m*(sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2))) ];
    [t, x] = ode45(f,[100,T],x0);
    Response_amp = (max(x(:,1)) - min(x(:,1)))/2;
%    xval(i) = Om/(2*pi) ; 
    xval(i) = l;
    yval(i) = Response_amp ; 
    zval(i) = d;
    end
    % plot(Om, Response_amp, '.');
end
plot3(xval,yval,zval) ; 
xlabel('length of spring (m)')
ylabel('Response Amplitude (m)')
zlabel('pretension (m)')
set(gca,'FontSize',13)

Hi, all. I wish to plot 3d grpah (length of spring vs response amplitude vs pretension). If run this code, I still get 2d graph. How am I supposed to do?

Thank you for your time.

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Answer 1

Ameer Hamza 2020-4-5

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/515493-how-do-i-plot-3d-graph#answer_424124

在 MATLAB Online 中打开

It is creating 3D line, but it is not visible because you run the hold(ax) at the beginning. Add the view(3) line like this to see the 3D view

fig = figure();
ax = axes();
view(3); % <--- add this
hold(ax);

Also, note that you are using i as a variable in both loops. I think this might be a mistake. Please check according to your program logic.

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Ameer Hamza 2020-4-5

在 MATLAB Online 中打开

Since you have two independent variables and one dependent variable, so you are trying to make a surface plot, I have refactored your code a bit. Try it

clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
l_array = linspace(0.1,1,100); %Excitation Amplitude
d_array = linspace(-0.1,-1,100);
[L_array, D_array] = meshgrid(l_array, d_array);
Response_amp = zeros(size(L_array));
T = 150;
x0 = [0,0];
for i=1:numel(l_array)
    for j=1:numel(d_array)
        l = L_array(i,j);
        d = D_array(i,j);
        k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
        
        f = @(t,x) [ x(2); ...
            -(2*k_s*(x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))* ...
            (sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2) - l))/ ...
            (m*(sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2))) ];
        
        [t, x] = ode45(f,[100,T],x0);
        Response_amp(i,j) = (max(x(:,1)) - min(x(:,1)))/2;
        %    xval(i) = Om/(2*pi) ;
    end
end
%% plot
fig = figure();
ax = axes();
view(3);
hold(ax);
% view([-53 33]);
grid on
mesh(L_array,D_array,Response_amp) ;
xlabel('length of spring (m)')
ylabel('pretension (m)')
zlabel('Response Amplitude (m)')
set(gca,'FontSize',13)

donghun lee 2020-4-5

在 MATLAB Online 中打开

Hi, sir. Can I ask you another quick question please?

%%
clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
%Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
l = 0.946;
d = -0.473;
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
Om_array = linspace(0,200,100); %Excitation Amplitude
A_array = linspace(0.1,1,100);
[Om_array, A_array] = meshgrid(Om_array, A_array);
Response_amp = zeros(size(Om_array));
T = 150;
x0 = [0,0];
for i=1:numel(Om_array)
    for j=1:numel(A_array)
        Om = Om_array(i,j);
        A = A_array(i,j);
        k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
        
        f = @(t,x) [ x(2); ...
            -(2*k_s*(x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))* ...
            (sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2) - l))/ ...
            (m*(sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2))) ];
        
        [t, x] = ode45(f,[100,T],x0);
        A = A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t);
        Response_amp(i,j) = (max(x(:,1)) - min(x(:,1)))/2;
        %    xval(i) = Om/(2*pi) ;
    end
end
%% plot
fig = figure();
ax = axes();
view(3);
hold(ax);
% view([-53 33]);
grid on
mesh(Om_array,A_array,Response_amp) ;
% xlabel('length of spring (m)')
% ylabel('pretension (m)')
% zlabel('Response Amplitude (m)')
a = colorbar;
a.Label.String = 'Response Amplitude (m)';
set(gca,'FontSize',15)

This is another code that I wish to plot, however if I run this code, it keeps saying that Index in position 2 exceeds array bounds. I don't understand what it means. How would I solve this problem?

Thanks!

Ameer Hamza 2020-4-5

在 MATLAB Online 中打开

Donghun, please check this code. I have modified your second code. This time I used a more robust approach

%%
clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
%Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
l = 0.946;
d = -0.473;
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
Om_array = linspace(0,200,100); %Excitation Amplitude
A_array = linspace(0.1,1,100);
[Om_array, A_array] = meshgrid(Om_array, A_array);
Response_amp = zeros(size(Om_array));
T = 150;
x0 = [0,0];
for i=1:size(Om_array,1)
    for j=1:size(Om_array,2)
        Om = Om_array(i,j);
        A = A_array(i,j);
        k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
        
        f = @(t,x) [ x(2); ...
            -(2*k_s*(x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))* ...
            (sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2) - l))/ ...
            (m*(sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2))) ];
        
        [t, x] = ode45(f,[100,T],x0);
        A = A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t);
        Response_amp(i,j) = (max(x(:,1)) - min(x(:,1)))/2;
        %    xval(i) = Om/(2*pi) ;
    end
end
%% plot
fig = figure();
ax = axes();
view(3);
hold(ax);
% view([-53 33]);
grid on
mesh(Om_array,A_array,Response_amp) ;
% xlabel('length of spring (m)')
% ylabel('pretension (m)')
% zlabel('Response Amplitude (m)')
a = colorbar;
a.Label.String = 'Response Amplitude (m)';
set(gca,'FontSize',15)

donghun lee 2020-4-5

在 MATLAB Online 中打开

Hi! Sorry, it was my fault. It just takes quite long to run. If you don't mind, can I ask you a last question?

%%
clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
l = 0.946;
d = -0.473;
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
%Om_array = linspace(0,200,100); %Excitation Amplitude
A_array = linspace(0,1,100);
% [Om_array, A_array] = meshgrid(Om_array, A_array);
Response_amp = zeros(size(A_array));
T = 150;
x0 = [0,0];
for i=1:size(A_array)
        A = A_array(i);
        k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
        
        f = @(t,x) [ x(2); ...
            -(2*k_s*(x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))* ...
            (sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2) - l))/ ...
            (m*(sqrt((l-d)^2 + (x(1)-(A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t)))^2))) ];
        
        [t, x] = ode45(f,[100,T],x0);
        A = A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t);
        Response_amp(i) = (max(x(:,1)) - min(x(:,1)))/2;
        %    xval(i) = Om/(2*pi) ;
    end
%% plot
fig = figure();
ax = axes();
%view(3);
hold(ax);
% view([-53 33]);
grid on
plot(A_array,Response_amp) ;
 xlabel('A (m)')
 ylabel('Response Amplitude (m)')
% zlabel('Response Amplitude (m)')
a = colorbar;
a.Label.String = 'Response Amplitude (m)';
set(gca,'FontSize',15)

In this code, I have defined that A = A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t). What I'm trying to do is to plot A vs Response_amp. However, this code makes Response_amp to be 0 all the way up to A = 1m. How could this happen?

Finally, I appreciate your efforts again.

Thanks, Ameer.

donghun lee 2020-4-5

在 MATLAB Online 中打开

If I make A to be used in my ode45, the code I have generated is as below,

clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
l = 0.946;
d = -0.473;
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
%Om_array = linspace(0,200,100); %Excitation Amplitude
A_array = linspace(0,5,100);
% [Om_array, A_array] = meshgrid(Om_array, A_array);
Response_amp = zeros(size(A_array));
T = 150;
x0 = [0,0];
for i=1:size(A_array)
        A = A_array(i);
        k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
        
        f = @(t,x) [ x(2); ...
            -(2*k_s*(x(1)-A))* ...
            (sqrt((l-d)^2 + (x(1)-(A))^2) - l)/ ...
            (m*(sqrt((l-d)^2 + (x(1)-(A))^2))) ];
        
        [t, x] = ode45(f,[100,T],x0);
        A = A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t);
        Response_amp(i) = (max(x(:,1)) - min(x(:,1)))/2;
        %    xval(i) = Om/(2*pi) ;
    end
%% plot
fig = figure();
ax = axes();
%view(3);
hold(ax);
% view([-53 33]);
grid on
plot(A,Response_amp) ;
 xlabel('A (m)')
 ylabel('Response Amplitude (m)')
% zlabel('Response Amplitude (m)')
a = colorbar;
a.Label.String = 'Response Amplitude (m)';
set(gca,'FontSize',15)

However, it says 'Vectors must be the same length'. I still don't get this.

Ameer Hamza 2020-4-5

在 MATLAB Online 中打开

See this code. I changed two lines

First line is for i=1:numel(A_array), please see the documentation of numel and size to see which one is appropriate in specific scenarios.
plot(A_array,Response_amp), A_array is 1x100 and Response_amp is also 1x100.

clc
clear all
A1 = 0.015; %Excitation Amplitude
A2 = 0.035;
A3 = 0.06;
l_r = 0.617; %Wave length of the road
v = 0.04107647433; %Speed(m/s)
P = l_r/v; %Period
Om = 1/P*2*pi; %Forcing Frequency
%Om = %0.07m,2m,45m/s
%Om = 9.512/(2*pi);
k_l = 26400; %Linear stiffness
m = 483; %Mass
l = 0.946;
d = -0.473;
%d = -0.1; %Stretching condition
f_n = sqrt(k_l/m)/(2*pi); %Natural frequency
%%
%Om_array = linspace(0,200,100); %Excitation Amplitude
A_array = linspace(0,5,100);
% [Om_array, A_array] = meshgrid(Om_array, A_array);
Response_amp = zeros(size(A_array));
T = 150;
x0 = [0,0];
for i=1:numel(A_array)
    A = A_array(i);
    k_s = -(k_l*(l-d))/(4*d); %Spring stiffness
    
    f = @(t,x) [ x(2); ...
        -(2*k_s*(x(1)-A))* ...
        (sqrt((l-d)^2 + (x(1)-(A))^2) - l)/ ...
        (m*(sqrt((l-d)^2 + (x(1)-(A))^2))) ];
    
    [t, x] = ode45(f,[100,T],x0);
    A = A1*sin(Om*t)+A2*sin(2*Om*t)+A3*sin(3*Om*t);
    Response_amp(i) = (max(x(:,1)) - min(x(:,1)))/2;
    %    xval(i) = Om/(2*pi) ;
end
%% plot
fig = figure();
ax = axes();
%view(3);
hold(ax);
% view([-53 33]);
grid on
plot(A_array,Response_amp) ;
xlabel('A (m)')
ylabel('Response Amplitude (m)')
% zlabel('Response Amplitude (m)')
a = colorbar;
a.Label.String = 'Response Amplitude (m)';
set(gca,'FontSize',15)