MATLAB: Trouble Understanding Code for a Hemisphere

hemisphere

I have used the following code to create a hemisphere with radius 10. Unfortunately I don't really understand what the code does, so if someone could explain this that would be great. Please try to be as detailed as possible, thanks.
figure (1)
[x,y,z]=sphere;
x=x(11:end,:);
y=y(11:end,:);
z=z(11:end,:);
r=10;
hemisphere=surf(r.*x,r.*y,r.*z);
axis equal

Best Answer

https://www.mathworks.com/help/matlab/ref/sphere.html
"sphere generates a sphere consisting of 20-by-20 faces."
so accessing the coordinates from 11 onwards would be only half of a sphere.
"The sphere function generates the x-, y-, and z-coordinates of a unit sphere for use with surf and mesh."
If you multiply coordinates based on the unit sphere by the radius of the sphere, then you get a sphere of that radius.
Then you draw the surface. After that you tell MATLAB that you want the x, y, and z axes to be the same spacing as each other (the default is to stretch the data to whatever the current size of the axes is.)
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