floor：朝负无穷方向舍入
B = floor(A) rounds the elements of A to the nearest integers less than or equal to A.
ceil：朝正无穷方向舍入
B = ceil(A) rounds the elements of A to the nearest integers greater than or equal to A.
fix：朝零方向舍入
B = fix(A) rounds the elements of A toward zero, resulting in an array of integers.
round：四舍五入
B = round(A) rounds the elements of X to the nearest integers.
Example：

a= [-0.9,    -2.1,    -0.4,    0.3,    0.8,    1.1,    2.7,    -1.2+2.9i];

floor(a)=[ -1,      -3,      -1,      0,      0,      1,      2,       -2+2i]

ceil(a)= [ 0,       -2,       0,      1,      1,      2,      3,       -1+3i]

fix(a)= [ 0,       -2,       0,      0,      0,      1,      2,       -1+2i]

round(a)=[-1,       -2,       0,      0,      1,      1,      3,       -1+3i]

注：For complex X, for all the four fuctions the imaginary and real parts are rounded independently.