[X, Y, Z] = cylinder // It returns the x, y, and z coordinates of a cylinder with a radius similar to 1. The cylinder has 20 similar spaced points around its circumference.
[X, Y, Z] = cylinder(r) // It returns the x, y, and z coordinates of a cylinder using r to describe a profile curve. cylinder treats each component in r as a radius at equally spaced heights along with the unit height of the cylinder. 
[X,Y,Z] = cylinder(r,n) // It returns the x, y, and z coordinates of a cylinder based on the profile curve described by vector r. The cylinder has n similar spaced points around its circumference.
cylinder(...) // with no output arguments, plot the cylinder using MATLAB surf.

r=sin?(3π z)+2
0≤z≤1,0≤θ≤2θ
z=[0: .02:1]';
r=sin(3*pi*z)+2;
cyclinder(r), axis square