Aiuto con il comando surf di una matrice di dati

Buongiorno,

ho una matrice di dati [x,y,z] e vorrei eseguire una rappresentazione 3d con barra di colore per la profondità lungo l'asse z. Ho provato con il comando

surf([x x], [y y], [z z], 'opzioni per il colore della faccia, del bordo ecc...')

dal momento che l'argomento z deve essere necessariamente una matrice, tuttavia oltre alla superficie che mi aspetto ce n'è un'altra indesiderata.

Answer 1

[saish]

Hi Vincenzo,

I observed that [x x] duplicates the column vector horizontally, but does not create a grid. The MATLAB ‘surf’ function expects X, Y, and Z to be matrices of the same size, where each (X(i,j), Y(i,j), Z(i,j)) is a point on the surface.

If the data is not on a grid, duplicating vectors does not create a real surface, it creates a flat “sheet” or an unwanted extra surface.

The MATLAB ‘meshgrid’ function can be used to create a grid of points covering a rectangular area in the x-y plane.

The function takes two vectors (x and y) as input and creates two 2D matrices: one containing all x-coordinates and the other containing all y-coordinates.

You can refer to the following code snippet, which uses the ‘surf’ function together with the ‘meshgrid’ function:

x = [1 2 3];
y = [4 5 6];
[X, Y] = meshgrid(x, y);
Z = [7 8 9; 10 11 12; 13 14 15]; % to match grid size

% Correct 3D surface plot
figure;
surf(X, Y, Z, 'FaceColor', 'interp', 'EdgeColor', 'none');
colorbar;
xlabel('X');
ylabel('Y');
zlabel('Z');

●

Additionally, for scattered data, you can use the MATLAB ‘griddata’ function which can interpolate the data onto a grid, which can be used with the ‘surf’ function.

You can refer to the following Matlab documentation and examples for reference.

https://www.mathworks.com/help/releases/R2022b/matlab/visualize/creating-3-d-plots.html

https://www.mathworks.com/help/releases/R2022b/matlab/ref/surf.html

https://www.mathworks.com/help/releases/R2022b/matlab/ref/meshgrid.html

https://www.mathworks.com/help/releases/R2022b/matlab/ref/griddata.html