function

Definition

       MATLAB The definition of the function in is as follows ：

function  Output parameters  =  Function name ( Input parameters )
   The body of the function 
end
%  Output parameter format 
% 1.  nothing  （function  Function name ( Input parameters )）
% 1.  Single variable （function y =  Function name ( Input parameters )）
% 2.  Array form （function [y1,y2,……] =  Function name ( Input parameters )）
%  Input parameter format 
% 1.  nothing  （function  Output parameters  =  Function name ()）
% 1.  Single variable （function  Output parameters  =  Function name (x)）
% 2.  Array form （function  Output parameters  =  Function name (x1,x2,……)）

In some places, you can define functions without end, But some must be added , Therefore, it is suggested to add end.

Taking array form as input parameter or function parameter is actually a single variable , It's just MATLAB The single variable of is also an array , Therefore, there is no need to worry about how to assign values if the output parameter is an array .

classification

        From the perspective of being called , Functions are divided into main functions and sub functions , The main function refers to the top in the file , Function with the same name as the file name ,（ Be careful ： The two conditions are actually fixed , Function file The first line in must be the function definition with the same name as the file name ） stay MATLAB in , Only the main function can be called by other files .（ in other words Call a function in a function file , Can and can only call the main function , And the main function name is the same as the file name ）

        From the perspective of particularity , Functions can be divided into four kinds ： Nested function 、 Anonymous functions 、 Private functions and overloaded functions .

Nested function

        Definition ： Functions defined within functions .
        effect ： It doesn't seem to work .

Nested functions can manipulate variables in parent functions .（ Here assume that the former is called the parent function ）

Anonymous functions

        The format of anonymous function is as follows ：

 Function name  = @( Variable 1, Variable 2,……)  expression 

        Be similar to C In language #define Function name ( Variable 1, Variable 2,……) expression , That is, through the function name and the corresponding variables , Return the value of the corresponding expression .

Command line windows are not allowed function Create a function , But anonymous functions are allowed .（ At least 2020 The version is like this ）

        Anonymous functions seem to be also called handle functions , But it is a little different from the function handle （ Pay attention to handle functions and function handles ）, Function handle refers to , Assign an existing function to another name , To complete the call of an existing function by another name , similar #define New name Existing function name ,MATLAB The method of implementing function handle is as follows ：

%  function BubbleSort
function y = BubbleSort(x)
len = length(x);
for m = 1 : len - 1
    for n = 1 : len - m
        if (x(n) > x(n + 1))
            [x(n), x(n + 1)] = deal(x(n+1), x(n));
        end
    end
    disp(['Sort step', num2str(m), ': ', num2str(x)])
end
y=x
end

%  Define the function above 
fun = @BubbleSort
%  here , Can pass fun Call function BubbleSort
x=[6,3,7,8,5,1,2,4,9]   % Define an array 
y = fun(x)  %  Equivalent to y = BubbleSort(x)

Private functions

        Private functions , That is, functions with access restrictions , The function file of the private function is located in private In the folder , As shown in the figure below x.m Functions are private functions , Private functions can only be called by files in the parent folder , The following is an example ,x.m Can only be y.m、Base.m A file called , Even if it is added to the file path , Can't be z.m、nua.m Wait for file call .

MATLAB For function access, please refer to MATLAB File path .

overloaded function

        overloaded function , stay MATLAB Middle refers to the same function name , But functions with different parameter types or numbers . Of course, there cannot be files of the same type with the same name in the same directory , Therefore, overloaded functions are generally located in different file directories .

        The definition of overloaded function is exactly the same as that of ordinary function , When called ,MATLAB The corresponding function will be called according to the parameter type .

file

file type

       MATLAB The files in can be divided into 3 Kind of , namely .m file ,.fig file ,.mat file .

.m file

       MATLAB Medium .m The document is similar to C In language .c file , It is used for storing MATLAB Code . Although the command line can also be executed , But it cannot be saved effectively , And if you are not careful, you will output a lot of information , Disrupt the formation .

       .m Files can be divided into script files and function files , The code in the script file can be executed in sequence （ That is, lines of code ）, In function files, keywords are used function start , Generally, input and output parameters are required , Therefore, even if you click Run, an error will be reported .（ If it is a function without input parameters , Even if there is a return value , It can also run successfully ）

Of course, there is actually no distinction between script files and function files , similar C Language , Has been main Function execution , Call other .c Functions in the file ,MATLAB Also the same , Always execute in the script file , It just calls the functions in the function file .

        stay MATLAB In the current folder window of the, you can find that the icons in front of the script file and the function file are different , As shown in the figure below , above BubbleSort.m For function file , Below TestBubbleSort.m The file is a script file .

        The following are the specific contents of the two documents , If opened BubbleSort.m File and click Run , The missing parameter... Will be displayed in the command line window , And open TestBubbleSort.m File and click Run , At this time, output after sorting normally .

（ When running, it should be under the corresponding path , At this time, the corresponding file should be visible in the current folder window ）

% BubbleSort.m file （ Function file ）
function y = BubbleSort(x)
len = length(x);
for m = 1 : len - 1
    for n = 1 : len - m
        if (x(n) > x(n + 1))
            [x(n), x(n + 1)] = deal(x(n+1), x(n));
        end
    end
    disp(['Sort step', num2str(m), ': ', num2str(x)])
end
y=x
end

% TestBubbleSort.m（ Script files ）
clc; %  Clear the command of the current command window 
clear; %  Clear memory 
x = randperm(9); %  take 1 To 9 These numbers are randomly scrambled and assigned to x
disp([' Data before sort: x = ', num2str(x)]);
disp('--------------------------------------');
y = BubbleSort(x); %  Call the bubble sort function to x Sort , The result is y
disp('--------------------------------------');
disp([' Data before sort: y = ', num2str(y)]);

There can be multiple functions in the function file , And script files can also write functions , Of course, the functions written in the script file cannot be at the top of the file （ I can't use function As the beginning of the file ）, When the script file calls a function , and a When the function is defined in this script file , Priority should be given to a Function instead of a function .（ decision .m Files are for code , According to the classification of so-called scripts and functions that are only available in code ）

Click the run button ,MATLAB Which script file to run depends on which file is currently open in the editor window , If you open a script file , Then execute the script file , If it is a function file , It will be based on whether there are input parameters , Decide to report an error or run .

.fig file

       MATLAB Medium .fig File is the user interface window definition file , It is used to define UI Interface file , adopt MATLAB After opening this type of file, the corresponding UI Interface , Operate at this time （ For example, click the button with the mouse ） The corresponding callback function will be called .

       .fig The creation of the file can be entered in the command line window guide, The following pop-up window pops up , Select the corresponding template and modify the path and file name , Then click OK to generate .

        here MATLAB The interface is shown in the figure below , You can see , Two files appear in the current folder window ,try.fig The document is UI Interface definition file ,try.m The corresponding callback function is stored in the file , For example, in UI Place a button in the interface , Then click , The code to be executed will be placed in try.m In the corresponding callback function in the file .

        About .fig file , Yes UI The use of the interface will be written in other articles .（ When you see this sentence , It means I haven't finished writing ）

.mat file

       .mat File is MATLAB File used to save data in , adopt save Functions and load Function can be completed .mat Operation of file , Store data in .mat file , And from .mat Export data from file , The example and explanation of the function are shown in the following table .

debugging

       MATLAB Enter the method of debugging , It seems that you can only set the breakpoint and click Run , Then start the corresponding debugging button , As shown in the figure below , Click... Next to the serial number in the editor window “-” To set breakpoints , When I hit run , Various debugging icons appear on the editor tab in the toolbar .

        Name of each icon 、 Shortcut key 、 The name is as follows .

Section commissioning

        There is no corresponding icon for section debugging , By entering two percent signs “%%” Segment the code , here Ctrl+Enter You can simply run the contents of this section .（ from %% To another %%, Click the corresponding section , The section highlights , The following figure 7~10 That's ok ）

        The addition and operation of sections can also be used without debugging , Move the mouse to the corresponding line , Right click and select “ Execute the current section (E)” or “ Insert section (I)”. Through section debugging, you can debug a piece of code alone .（ Of course, you may want to pay attention to the variables used in this section , And it seems that private functions cannot be used ）

Step by step debugging

        After debugging through breakpoints , You can perform one-step debugging , Single step debugging can pass surface Buttons in （ Or by shortcut keys ） Run the code line by line , See the effect .