Is what I have correct?
a = 2;
b = 1;
% x = a*cos(phi)*cos(theta);
% y = b*cosphi*sintheta;
% z = b*sinphi;
xb = a;
yb = b;
zb = b;
[x,y,z] = ellipsoid(0,0,0,xb,yb,zb);
figure;
surf(x, y, z);
axis equal;
% The max possible value for x = semi-radius of x = a
% The max possible value for y = semi-radius of y = b
% max possible value for z = semi-radius of z = b