ischar
tf = ischar(A) %判断是否为字符数组
returns logical 1 (true) if A is a character array and logical 0 (false) otherwise.
isstring
tf = isstring(A) %判断是否为string
returns 1 (true) if A is a string array. Otherwise, it returns 0 (false).
isnumeric
tf = isnumeric(A) %判断是否为数值型数据。数值型数据有：single,double,int等
returns true if A is a numeric array and false otherwise.
max
M=max(A)
M=max(A,[],dim)
[M,I]=max(A) %返回最大值和对应索引
