Blank plot in matlab

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MOUNIBA REDAH 2019-6-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468793-blank-plot-in-matlab

评论： Star Strider 2019-6-27

采纳的回答： Star Strider

在 MATLAB Online 中打开

hello can you please help me?? when i type this code i only get a balnk plot

i don`t know where is my mistake

the code

sigma0=0;
el= 0.5;
L= 1 ;
h= 0.5 ;
a= 1;
N= 3;
g=10;
rho=1000;
Z0=0;
t=0:0.01:5;
x=0:0.02:el;
y=0:0.02:L;
[X,Y]=meshgrid (x,y);
sigma=0;
T=3*pi/4;
for n=0:N
    for m=0:N
        A=pi*((m/el)^(2)+(n/L)^(2))^(0.5);
        B=(g*A+(sigma/rho)*A^3)*atan(A*h);
        C=B^(0.5); 
        Z=a*cos(C.*T).*cos((m*pi/el).*X).*cos((n*pi/L).*Y);
        Zs=Z0+Z;
        Z0=Zs;
       
    end
end
  m=3;
  n=4;
    
A=pi*((m/el)^(2)+(n/L)^(2))^(0.5);
B0=(g*A+(sigma0./rho)*A^3)*atan(A*h);
C0=(B0.^(0.5)); 
Z0=(a.*cos(C0.*T)).*cos((m*pi/el).*X).*(cos((n*pi/L).*Y));
figure
subplot(221)
plot(t,length(Z0));
xlabel(' temps s');
ylabel(' élévation z(x,y)y');
title(' sans tension superficielle');
legend('sigma0')

采纳的回答

Star Strider 2019-6-25

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468793-blank-plot-in-matlab#answer_380708

在 MATLAB Online 中打开

The immediate problem is:

plot(t,length(Z0));

since the length function will produce a scalar, and you can only plot a scalar using a marker. (The plot function plots lines between two defined points, and a scalar has only one.)

Beyond that, however, ‘Z0’ is not a function of ‘t’, and has entiely different dimensions as the result, so you cannot plot it as a function of ‘t’.

This works:

plot(Z0);

however it is likely not the result you want. You need to fix that problem.

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MOUNIBA REDAH 2019-6-25

编辑：MOUNIBA REDAH 2019-6-25

The wavenumbers A are worth: A=pi*((m/el)^(2)+(n/L)^(2))^(0.5)

(m, n) are two positive integers whose mode of vibration is determined with a pulsation given by the following dispersion relation: (B)^2=(g*A+(sigma./rho)*A^3)*atan(A*h)

The elevation of the free surface is given by:Z(x,y,t)=(a.*cos(B.*T*t)).*cos((m*pi/el).*x).*(cos((n*pi/L).*y))

The expression obtained shows that all the fluid particles lying on the free surface vibrate in phase, but the amplitude of these sinusoidal movements depends on the spatial coordinates x and y.

time dependence is assumed to be harmonic in which the velocity potential satisfies the initial condition Z (x, y,0) = 0.

For a given value of x the surface of the liquid moves up and down, and for a given value of time t, the shape of the surface is a cosine curve, such a wave does not propagate . In fact, the free surface oscillates vertically. As in the case of the eigenmodes of the vibration of a solid structure, the sloshing modes appear as stationary surface waves due to the confinement of the liquid by the walls of the reservoir.

my goal is to study tthe effect of sigma on Z in a time t

Star Strider 2019-6-25

在 MATLAB Online 中打开

You can easily do that for individual values of ‘x’ and ‘y’ as a function of ‘t’.

I would just do this:

sigma0=0;
el= 0.5;
L= 1 ;
h= 0.5 ;
a= 1;
N= 3;
g=10;
rho=1000;
Z0=0;
t=0:0.01:5;
x=0:0.02:el;
y=0:0.02:L;
[X,Y]=meshgrid (x,y);
sigma=0;
T=3*pi/4;
% for n=0:N
%     for m=0:N
%         A=pi*((m/el)^(2)+(n/L)^(2))^(0.5);
%         B=(g*A+(sigma/rho)*A^3)*atan(A*h);
%         C=B^(0.5); 
%         Z=a*cos(C.*T).*cos((m*pi/el).*X).*cos((n*pi/L).*Y);
%         Zs=Z0+Z;
%         Z0=Zs;
%        
%     end
% end
  m=3;
  n=4;
    
A=pi*((m/el)^(2)+(n/L)^(2))^(0.5);
B0=(g*A+(sigma0./rho)*A^3)*atan(A*h);
C0=(B0.^(0.5)); 
Z0=(a.*cos(C0.*T)).*cos((m*pi/el).*X).*(cos((n*pi/L).*Y));
figure
subplot(221)
hold all
for k1 = 1:numel(x)
    for k2 = 1:numel(y)
        Z0=(a.*cos(C0.*T*t)).*cos((m*pi/el).*x(k1)).*(cos((n*pi/L).*y(k2)));
        plot(t, Z0)
    end
end
xlabel(' temps s');
ylabel(' élévation z(x,y)y');
title(' sans tension superficielle');
legend('sigma0')

That at least produces a plot of ‘Z0’ as a function of ‘t’ for all values of ‘x’ and ‘y’.

That is the best I can do.

MOUNIBA REDAH 2019-6-27

编辑：MOUNIBA REDAH 2019-6-27

CODE.txt

hello Star Strider a colegue had help me and give me some information the reason of Loops in my code is because there is a summuation in my equation

And gave me the code of It only It is not using Plot ,This example in using SURF because the result that gave me is in 3D

My qustion it is possible to modify in this code in order to plot the graph I Want I mean to change the eqaution above by this one :

Ps The code attached

Star Strider 2019-6-27

在 MATLAB Online 中打开

I have no clue as to what you want.

Try this:

t = linspace(0, 1);                                 % Use Correct Time Limits
omega = rand(4);                                    % Use Correct Values
for k1 = 1:4
    for k2 = 1:4
        Z(k1,k2,:) = acos(omega(k1,k2)*t);
    end
end
Zs = sum(sum(Z,2),1);
Zs = squeeze(Zs);
figure
plot(t, Zs)