How to cut off 1/4 of half sphere

Hello! I'm a rookie in Matlab worId... I want to make an illustration of 3/8 of a sphere (this is, just 3/4 of the upper half) but I would like to do it without changing the current axis limits. Anyone can help, please? Thanks a lot! Have a nice day! (:

Target:

Current:

Current code:

[x y z]=sphere;
r=378; 
surf(r*x,r*y,r*z+81.250);

xlabel('x axis [mm]')
ylabel('y axis [mm]')
zlabel('z axis [mm]')

Answer 1

[Cris LaPierre]

Set the corresponding quadrant values equal to nan. There are several ways to do this. Here is one.

[x y z]=sphere;
x(11:end,1:5)=nan;

r=378; 
surf(r*x,r*y,r*z+81.250);

[Francisco Cruz]

Perfect! Thank you so much!