How to connect 3d plot lines with a surface?

I have matlab code that will plot a 3d line for each group of data points that I specify. Now I want to create a surface that connects all of the plot lines. Like a trend line for data in excel, but in this case I need it to be a surface not a line. How can I do that?

Initially I tried using surf, but the plot it returned was very choppy and not a smooth surface. However that was before I split the data into groups. (plot3 used to give me a zigzag line before I split the data into groups). I am currently using a loop to group my data and plot each line, but I'm struggling with applying that to creating a surface (you can see in the code below that I tried a surf within the loop but commented it out).

if true
data = xlsread('NeedleTest.xls') ;
x=data(:,1);
p=[0.05 0.1 0.03 0.07 0.08 0.09 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2];
hold on
grid on
count=1;
while count<numel(p); 
m=find(x==p(count)); 
      data2=data(m,1:3); 
      %s=scatteredInterpolant(data2(:,1), data2(:,2), data2(:,3))
      %[X Y]=meshgrid(data2(:,1), data2(:,2))
      %s=surf(X,Y,data2)
      plot3(data2(:,1), data2(:,2), data2(:,3))
      count=count+1;
end
xlabel('Percent Open')
ylabel('Pressure H2O')
zlabel('Flow lpm')

Answer 1

[Jacob Mathew]

Hi Julia,

You can utilise the meshgrid function to create the surface that you want. Here is an example:

% Sample data for three lines
x = 1:10;
y1 = rand(1, 10);
y2 = rand(1, 10) + 1; 
y3 = rand(1, 10) + 2; 

z1 = linspace(0, 1, 10);
z2 = linspace(1, 2, 10);
z3 = linspace(2, 3, 10);

% Plotting the lines by itself
figure;
plot3(x, y1, z1, '-o', 'DisplayName', 'Line 1', 'LineWidth', 2);
hold on;
plot3(x, y2, z2, '-x', 'DisplayName', 'Line 2', 'LineWidth', 2);
plot3(x, y3, z3, '-s', 'DisplayName', 'Line 3', 'LineWidth', 2);
xlabel('X-axis');
ylabel('Y-axis');
zlabel('Z-axis');
title('3D Lines');
legend;
grid on;
view(3);

% Combine y and z data into matrices for surface plotting
Y = [y1; y2; y3];
Z = [z1; z2; z3];

% Create a meshgrid for x values
[X, Zgrid] = meshgrid(x, [0 1 2]);

% Plot the surface and the lines
figure;
surf(X, Y, Z, 'FaceAlpha', 0.5); % transparency for better visibility of lines
hold on;
plot3(x, y1, z1, '-o', 'DisplayName', 'Line 1', 'LineWidth', 2);
plot3(x, y2, z2, '-x', 'DisplayName', 'Line 2', 'LineWidth', 2);
plot3(x, y3, z3, '-s', 'DisplayName', 'Line 3', 'LineWidth', 2);
xlabel('X-axis');
ylabel('Y-axis');
zlabel('Z-axis');
title('3D Surface Connecting Lines');
legend;
grid on;
view(3);

You can reference the documentation for meshgrid in the link below:

https://www.mathworks.com/help/releases/R2024a/matlab/ref/meshgrid.html