How to generate plot of a function?

I have the code:

function [ z ] = fun( )
%FUN Produces 3D surface plot with contours below the surface of f(x)

dx=0.1*pi;

x=linspace(0,nx*dx,nx);
y=linspace(0,nx*dx,nx);

wave1=makewave([1,0],sin);
wave2=makewave([0,1],cos);
wave3=makewave([200,20],sin);
wave4=makewave([1,1],sin);

z=wave1+wave2+wave3+wave4;

surfc(x,y,z);
title('Some Waves')
xlabel(x)
ylabel(y)
zlabel('amplitude')

end

function [ wave ] = makewave( coefs, wavefun )
wave=wavefun(coefs(1)*x+coefs(2)*y);
end

That should produce a 3D surface plot of f(x)=sin(x)+cos(y)+sin(20y)+sin(x+y)

And:

When nx=100

How do I define nx if nx is also an input?

Answer 1

[OCDER]

It was almost right, but a few things needed some changes. See comments in the code. To run this on the command line:

>> nx = 100; %nx defined OUTSIDE the function is a different variable than the nx inside fun.
>> z = fun(nx);

Here is the edited function that should get you what you want now:

function [ z ] = fun(nx) %specify input to fun as nx
%FUN Produces 3D surface plot with contours below the surface of f(x)
dx=0.1*pi;
x=linspace(0,nx*dx,nx);
y=linspace(0,nx*dx,nx);
[X, Y] = meshgrid(x, y); %You need a 2D matrix to use surfc.
wave1=makewave(X, Y, [1,0], @sin); %To pass a function, use function handle @sin
wave2=makewave(X, Y, [0,1], @cos); 
wave3=makewave(X, Y, [200,20], @sin); 
wave4=makewave(X, Y, [1,1], @sin); 
z=wave1+wave2+wave3+wave4;
surfc(x,y,z);
title('Some Waves')
xlabel('x') %must be a string, 'x'
ylabel('y') %must be a string, 'y'
zlabel('amplitude')
end

function [ wave ] = makewave(X, Y, coefs, wavefun) %you need to pass X and Y as inputs too.
wave=wavefun(coefs(1)*X+coefs(2)*Y);
end

[amateurintraining]

Thank you so much!

[OCDER]

You're welcome!