Modeling essential: matlab commonly used functions

String processing

int2str

Convert integer to string

a=int2str(k)

str2int

Convert string to integer

k=str2int(a)

strcat

Concatenate several strings together

a=strcat('hello',' ','world');

Matrix processing

size

Get the number of rows and columns of the matrix

[row,col]=size(a);
s=size(a,1); % 返回矩阵行数
s=size(a,2); % 返回矩阵列数

length

Count the number of elements in a one-dimensional array

s=length(a);

intersect

Calculate the same elements of two arrays (if an element appears repeatedly, it will only be counted once)

c=intersect(a,b);

find

Find the eligible element in the array or matrix and return its index value. (If it is a matrix, return the index value of the column storage code)

% 找到不为0的元素
>> X = [1 0 4 -3 0 0 0 8 6];
>> ind = find(X)

ind =

     1     3     4     8     9
     
% 找到满足条件的元素
>> X = [1 0 4 -3 0 0 0 8 6];
>> ind = find(X == 4)

ind =

     3
 
% 判断是否存在某元素
>> if isempty(find(X == 9))
        log = 0
    else
        log = 1
    end

log =
     0

data processing

sum

% 对该列所有元素求和
sum(a(:,col));

mean

m=mean(A);
% 若A是向量则返回A中值的平均值，若是矩阵则返回每一列的平均值

mad

Median number

m=mad(A);

std

Find the standard deviation.

s=std(A);