You can use the surf plot to visualize a spatial diagram for cross diffusion in MATLAB. The surf function creates a 3D surface plot, where the x and y coordinates represent the spatial domain, and the z coordinate represents the concentration or any other quantity of interest.
Here's an example code snippet,
title('Spatial Diagram for Cross Diffusion');
In this example, X and Y define the meshgrid for the spatial domain, and u represents the concentration. The surf function is used to create the 3D surface plot, with the x and y coordinates provided by X and Y, and the z coordinate provided by u.
In addition to the surf functions, there are several other plots you can use to create a spatial diagram for cross diffusion in MATLAB.
You can refer to the below documentation on plots for more information on plots,
Hope this helps!