Matlab | basic knowledge summary I

 Matlab Basics

 Matlab   The general form of a statement ：

Variable  = expression

Evaluate the value of an expression , And assign the result to the assignment number “=” The variable on the left

Matlab  Execution of command ： enter

Matlab All commands and built-in functions are composed of lowercase letters

Matlab   Naming rules for variables ：

• Start with a letter ;

• By letter 、 Numbers and underscores ;

• Letters are case sensitive ;

• Don't be too long , Generally, do not exceed  63  Characters

  Common function keys

System predefined variables

Special variables ：ans

Matlab   The number in ：

① The default is double precision real numbers ;

② It can be expressed in floating-point form or scientific counting ;

③ The range of real numbers that can be represented is ：10-308   ~ 10308;

④ The relative error of floating-point operation is  eps, about  2.2  10- 16;

⑤  Plural input ：z=3+4i, Pay attention to the imaginary part and  i  There must be no space between them

Basic operation and priority

Special symbols

Command separator ： Comma or semicolon

If you don't want to display the results on the screen , Semicolon can be used as statement terminator

System operation command

Workspace and search path management

 Matlab All punctuation marks in must be entered in English !

Matrix operations

Matlab： Matrix lab , Take matrix as basic operation unit , stay  Matlab in , Everything is a matrix    matrix

Direct input ： Such as  A=[1 2 3; 4,5,6]

①  In square brackets “[ ] ”;

② The elements in the same line are separated by spaces or commas ;

③ Lines are separated by semicolons

The special function of colon ：a:b:c %  Generate a vector that satisfies the arithmetic sequence

① a  It's the first ,b  It's tolerance , c  Determine the last item ( Not necessarily the last item );

②  If the tolerance is  1, It can be abbreviated as  a:c

References to matrix elements

Delete the specified row or column

Common matrix generating functions

Basic matrix operations

① Addition and subtraction ：A+B,A ‐B, Operate on the components

② Ordinary multiplication ：A*B

③ division ：A\B Equivalent to  A‐1B,A/B Equivalent to  AB‐1

④  Power operation ：A^p, namely  p  individual  A  Multiply , A  It's the square , p  It's a positive integer.

⑤ The transpose of the matrix ：A'( Conjugate transpose ),A.'( Normal transpose , Do not take conjugation )

Array operation of matrix ： Operate on the corresponding elements , Including dot multiplication ( .*), Point division ( ./ .\), Point power ( .^)

① There cannot be spaces between points and arithmetic operators

② The objects participating in the operation must have the same shape

Matrix  Kronecker  The product of ：kron(A,B)

The flip and rotation of matrix

Change the shape of the matrix and check the size of the matrix

The value of the function acting on the matrix ： set up  f Is the function ,x It's a variable. ( It can be a vector or a matrix )

①f(x) It's about x On each component of ;

②  if x It's a matrix , be  f(x) It's a relationship with x Matrices of the same shape

  

Matrix and number operation

① Addition and subtraction ： Every element of the matrix adds and subtracts with numbers ;

② Matrix times a number ： Every element of the matrix is multiplied by numbers ;

③ Matrix divided by a number ： Each element is divided by this number ;

④ Number and matrix point power operation ： Use array operation , Such as  2.^[1,2,3;4,5,6]

Output format of variable ：format

① When outputting the calculation result on the screen , Can pass  format  Command specifies the output format ;

② format   Only change the output format , Does not change the value of the variable ;