# Plot a function of two variables

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SA on 13 Mar 2021
Commented: SA on 13 Mar 2021
I want to plot the function sin(4*pi*x)*sin(4*pi*y).
I tried the following but I am not sure if I am doing the right thing. Any help will be appreciated. Thanks
h = 2/11;
x = -1+h:h:1-h;
y = x;
[X,Y] = meshgrid(x,y);
z = @(x,y) sin(4*pi*x).* sin(4*pi*y); % Create Function
plot(x, z(X,Y))
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SA on 13 Mar 2021
The function sin(4*pi*x)*sin(4*pi*y) is the exact solution to a Poisson equation and I want to plot the exact solution given the domain -1<=x<=1 and -1<=y<=1 and a dimension of 11 in both directions.

Cris LaPierre on 13 Mar 2021
I think you want to plot a surface rather than a line plot. Use surf with inputs X, Y and z. This will allow you to see the response over the full X-Y parameter space. Since the number of points will affect the resolution of this surface, I use linspace instead of the colon operator.
h = 2/11;
x = linspace(-1+h,1-h,50);
y = x;
[X,Y] = meshgrid(x,y);
z = @(x,y) sin(4*pi*x).* sin(4*pi*y); % Create Function
surf(X,Y,z(X,Y)) SA on 13 Mar 2021
Thank you