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MATLAB tutorial: how to plot a function of two variables
Math 331, Fall 2016 * Vitor Matveev * Lecture 1
We will make a simple plot of the following paraboloid (for x in [-2, 2])
u(x,y) = 1 - x^2 - y^2
Note that just a couple lines accomplish this task:
L = 2; % Define the size of coordinate box x = linspace(-L, L, 20); % Create an array of "x" coordinates in [-L, L] y = linspace(-L, L, 20); % Create an array of "y" coordinates in [-L, L] [X, Y] = meshgrid(x, y); % Make an [X, Y] grid (mesh) using (x, y) above U = 1 - X.^2 - Y.^2; % IMPORTANT: note the periods "." in operations surf(X, Y, U); % surf plots the surface xlabel('x'); ylabel('y'); zlabel('U(x,y) = 1 - x^2 - y^2'); title('This is a simple plot of u(x,y) = 1 - x^2 - y^2');
Alternative method of visualization: level curves / contour plot
hold off; contourf(X, Y, U); % Filled Contour plot of same function xlabel('x'); ylabel('y'); zlabel('U(x,y) = 1 - x^2 - y^2'); title('A contour (level set) plot of u(x,y) = 1 - x^2 - y^2');
