What did you get when you ran it? Whether it's "right" depends on what the goal is.
% this plots the surface over both x and y
% z is invariant over y
x = linspace(0,2*pi,300);
[x,y]=meshgrid(x); % spelled right
z = sin(x);
surf(x,y,z)
% this plots z for y=0
x = linspace(0,2*pi,300);
y = zeros(size(x));
z = sin(x);
plot3(x,y,z)
Depends what you want.
