Surf plot Mesh Plot

Respected Sir,

I have three parameters P, Q and R all having 216 values and none is dependent on other (all are obtained independently)

Kindly let me know if I can plot surf/grid plot with these values. If not, any other plot except using trisurf command.

Excel file is attached herewith.

Thanks in advance.

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/5468-construct-volumetric-mesh-grid-by-interpolating-scattered-point-cloud

or modify https://www.mathworks.com/matlabcentral/fileexchange/38858-contour-plot-for-scattered-data

Answer 1

[Abhishek]

Hi @Anshul Jain

It is my understanding that you want to generate a 3D surface plot from independently obtained variables ‘P’, ‘Q’, and ‘Lx’, where the data is not arranged on a structured grid in MATLAB.

In such cases, MATLAB’s ‘surf’ function cannot be used directly on raw data. This is because ‘surf’ expects data to be arranged on a uniform grid, whereas your data points are scattered. However, by interpolating the scattered values onto a regular grid, it is possible to visualize the surface using ‘surf’, without resorting to ‘trisurf’. To handle this, I used MATLAB’s ‘scatteredInterpolant’ function, specifically designed to interpolate scattered data onto a grid.

Here’s a simple step-by-step guide to do this:

• Load and extract data: Extract the three columns and assign them to three variables corresponding to ‘P’,’Q’, and ‘Lx’.
• Construct a surface interpolation model: Since the data points are scattered and not arranged on a grid, ‘scatteredInterpolant’ is used to construct a surface interpolation model:

F = scatteredInterpolant(P, Q, Lx, 'natural', 'none'); 

• Generate a regular grid in the domain of P and Q: This step defines the structure on which to evaluate the interpolated values:

p_lin = linspace(min(P), max(P), 50);  
q_lin = linspace(min(Q), max(Q), 50); 
[PP, QQ] = meshgrid(p_lin, q_lin); 

• Evaluate interpolated values on the grid: Use the interpolation function to compute ‘Lx’ over the defined grid:

RR = F(PP, QQ); 

• Visualisation: The interpolated data is now in a format compatible with ‘surf’, allowing the surface to be plotted:

surf(PP, QQ, RR) 
xlabel('P (Radian)') 
ylabel('Q (Radian)') 
zlabel('Lx (mm)') 
title('Interpolated Surface from Scattered Data') 
shading inte

I tried it on MATLAB R2024b, here is the output:

As you can see above, the mentioned approach successfully generated the desired surface plot.

For further reference on ‘scatterInterpolant’ and ‘surf’ methods, refer to the official MATLAB documentation:

• ‘scatterInterpolant’: https://www.mathworks.com/help/releases/R2024b/matlab/ref/scatteredinterpolant.html
• ‘surf’: https://www.mathworks.com/help/releases/R2024b/matlab/ref/surf.html

Hope this helps!