MATLAB: How to create a 3D contour Plot from X,Y,Z table

contourMATLABsurface

I have a table an X,Y,Z table extracted from STAR-CCM over the surface of an object. The X,Y,Z dat corresponds to Pressure, X -Position, and Z-Position. Each X,Z coordinate has a corresponding Pressure value.

How do I plot a surface plot of this?

Attached is the data I'm using.

Best Answer

Try this:

d = csvread('Cell Surface Pressure.csv');
p = d(:,1);
x = d(:,2);
z = d(:,3);
xv = linspace(min(x), max(x), 1000);
zv = linspace(min(z), max(z), 1000);
[X,Z] = meshgrid(xv, zv);
P = griddata(x, z, p, X, Z);
figure
scatter3(x, z, p, '.')
grid on
figure
meshc(X, Z, P)
grid on
figure
contourf(X, Z, P)
grid on

The first figure is a scatter plot of your original data,.the second a surface rendering with a contour, and the third, a filled contour plot.

Related Solutions

MATLAB: How i can solve this problem? Pleas!

Your ‘T’ matrix must become a cell array. See my sample of ‘T’ for an example.

Once you do that, I would do something like this:

Y = [12.004
    13.1573 
    11.1665  
    11.8082    
    12.2129   
    12.8075   
    12.4167  
    11.5708   
    12.5798    
    13.7489];
T={'cluster2'; 'cluster1'; 'cluster3'; 'cluster9'; 'cluster0'; 'cluster7'; 'cluster4'}; % Sample Of Cell Array
[UnqClust,~,idx] = unique(T);                                                           % Unique Values & Locations
Out = Y(idx);                                                                           % Mapped Output
for k1 = 1:length(idx)
    fprintf(1, '\t%s\t%.4f\n', T{k1}, Out(k1))              % Demonstration Output (Delete Loop)
end
  cluster2  11.1665
  cluster1  13.1573
  cluster3  11.8082
  cluster9  12.4167
  cluster0  12.0040
  cluster7  12.8075
  cluster4  12.2129

MATLAB: How to create a 2D contour Plot from X,Y,Z table

The first issue is that one of your inputs to griddata is symbolic. It must be numeric. Use the double function to convert Qs1 to doubles.

P = griddata(Lp_x11, Vs, double(Qs1), X, Z);

Next, your scatter3 function call does not use variables that exist. Variables are case sensitive. Use X, Z and P. In addition, the inputs to scatter3 must be vectors, not arrays. Use a colon to turn your arrays into vectors.

scatter3(X(:), Z(:), P(:), '.')

Surface plots (meshes, contours) will not work with the data as you currently have it since the data is more of a line than a surface. You have gridded the data, but most of the values are NaN. Scatter3 may be the best choice.

You could also try just plotting in 3D.

plot3(Lp_x11, Vs, double(Qs1))

Upon closer inspection, you'll see that you are ony solving you equation along the diagonal (Vs(i),Lp_x11(i)). This is why your results of all NaN. You are essentially trying to determine an entire surface from a single line. Instead, you want to user your loop to pick one value (say Vs(i)), and solve for all values of Lp_x11. If you capture the results correctly, Qs1 and Qs2 will be num x num arrays.

At that point, you want to use interp2, not gridded data, to increase the resolution of your data.

Here's your code modified.

num=50;
Lpmax=700e-6;
Lpmin=20e-6;
Lr=2.77e-3;
Cr=2.5e-9;
f=1/(2*pi*sqrt(Lr*Cr*0.5));
w=2*pi*f;
T=1/f;
Tdead=T*0.011;
Lp_x11=linspace(Lpmin,Lpmax,num);
Vs=linspace(140,340,num);
Vo=180;
Re_x11=200;
theta=0;
% solve the D
syms D11
theta_dch=(2*pi*Tdead)/T;
for r=1:length(Vs)
    X=vpasolve(sin(D11*pi)/(2*(1-D11))-Vo/Vs(r));
    D_ch=X;
    A2=(1./(Re_x11.*(pi.^2).*(1-D_ch))).*2.*w.*Lp_x11.*sin(pi.*D_ch).*sin(pi.*(1-D_ch));
    Qlr1=(2.*Vs(r).*sin(pi.*D_ch)./(Re_x11.*pi.*(1-D_ch).*w)).*(sin(-pi.*D_ch-theta_dch)-sin(-pi.*D_ch));
    Qlr2=(2.*Vs(r).*sin(pi.*D_ch)./(Re_x11.*pi.*(1-D_ch).*w)).*(sin(pi*D_ch-theta_dch)-sin(pi.*D_ch));
    Qlp_S1=-(1./w).*(Vs(r).*theta_dch./(w.*Lp_x11)).*(A2./(1-D_ch)-pi.*D_ch+theta_dch./2);
    Qlp_S2=(1./w).*(D_ch.*Vs(r).*theta_dch)./(w.*Lp_x11.*(1-D_ch)).*(A2./D_ch+pi.*(1-D_ch)-theta_dch./2);
    
    % Vs will be the y axis, which corresponds to the rows of the matrix
    % Capture the entire row of data using the indexing below.
    Qs1(r,:)=Qlp_S1+Qlr1; 
    Qs2(r,:)=Qlr2+Qlp_S2;
end
xv = linspace(min(Lp_x11), max(Lp_x11), 1000);
zv = linspace (min (Vs), max (Vs), 1000);
[X,Z] = meshgrid(xv, zv);
% P = griddata(Lp_x11, Vs, double(Qs1), X, Z);
P = interp2(Lp_x11, Vs, double(Qs1), X, Z);
figure
scatter3(X(:), Z(:), P(:), '.')
grid on
figure
meshc(X, Z, P)
grid on
figure
contourf(X, Z, P)
grid on

Best Answer

Related Solutions

MATLAB: How i can solve this problem? Pleas!

MATLAB: How to create a 2D contour Plot from X,Y,Z table

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