Matlab学习笔记--常用命令

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前言

Matlab常用命令。

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一、基本操作与矩阵输入

1.数据类型

logical
char
numeric:
  int8、uint8、single、double
  int16、uint16、
  int32、uint32、
  int64、uint64
  默认数据类型double
cell
struct

2.优先级

Variable
Built-in function
SubFunction
Private function:
  MEX-file
  P-file
  M-file

3.Format

Style	Example
short	3.1416
long	3.141592653589793
shortE	3.1416e+00
longE	3.141592653589793e+00
bank	3.14
hex	400921fb54442d18
rat	355/113

4.Array Indexing

索引从1开始计数。

A = [1 21 6;
		 5 17 9;
		 31 2 7]
A(8) = 9
A([1 3 5]) = 1 31 17
A([1 3;1 3]) = 1 31;1 31
A(3,2) = 2
A([1 3],[1 3]) = 1 6;31 7

5.Colon Operator

1到100

A = 1:100

6.特殊矩阵

eye(n):对角线矩阵
zeros(n1,n2)：n1n2零矩阵
ones(n1,n2)：n1n2全1矩阵
diag()：diagonal矩阵
rand()：随机矩阵

7.矩阵相关函数

max(A)
max(max(A))
min(A)
sum(A)
mean(A)
sort(A)
sortrows(A)
size(A)
length(A)
find(A)

二、结构化程序和自定义函数

1.Flow Control

if,elseif,else	Execute statements if condition is true
for	Execute statements specified number of times
switch,case,otherwise	Execute one of several groups of statements
try,catch	Execute statements and catch resulting errors
while	Repeat execution of statements while condition is true
break	Terminate execution of for or while loop
continue	Pass control to next iteration of for or while loop
end	Terminate block of code,or indicate last array index
pause	Halt executionnn temporarily
return	Return control to invoking function

2.相关逻辑运算

Opeerator	Meaning
<	Less than
<=	Less than or equal to
>	Greater than
>=	Greater than or equal to
==	Equal to
~=	Not Equal to
&&	And
ll	Or

3.if elseif else

if condition1
	statement1
elseif condition2
	statement2
else
	statement3
end

4.switch

switch expression
case value1
	statement1
case value2
	statement2
.
.
otherwise
	statement
end	

5.while

while expression
	statement
end

6.for

for variable= start:increment:end
	commands
end

7.break

在while中直接跳出循环到达end

x = 2;k = 0;error = inf;
error_threshold = 1e-32;
while error > error_threshold
	if k > 100
		break
	end
	x = x - sin(x)/cos(x);
	error = abs(x - pi);
	k = k+ 1
end

8.小技巧

clear all 清除所有变量
close all 关闭所有图形窗口
；隐藏命令窗口输出
… 换行
Ctrl + C终止运行脚本

9.自定义函数

自由落体

function x = freebody(x0,v0,t)
x = x0 + v0.*t + 1/2*9.8*t.*t;

10.多输入输出函数

function [a,F] = acc(v2,v1,t2,t1,m)
a = (v2-v1)./(t2-t1);
F = m.*a;

11.Function Defaullt Varialbes

inputname	Varialbe name of function inpu
mfilename	File name of currently running function
nargin	Number of function input arguments
nargout	Number of function output arguments
varargin	Variable length input argument list
varargout	Variable length output argument list

12.Function Handles

f = @(x) exp(-2*x);
x = 0:0.1:2;
plot(x,f(x));

三、变量与存取

1.数据类型转换

函数	功能
double()	转换成double类型
single()	转换成单精度
int8()	转换成8位符号整型
int16()	转换成16位符号整型
int32()	转换成32位符号整型
int64()	转换成64位符号整型
uint8()	转换成8位无符号整型
uint16()	转换成16位无符号整型
uint32()	转换成32位无符号整型
uint64()	转换成64位无符号整型

2.Character(char)

s1 = 'h'
whos
uint16(s1)
s2 = 'H'
whos
uint16(s2)

3.String

s1 = 'Example';
s2 = 'String';
字符串拼接
s3 = [s1 s2];
s4 = [s1;s2];

4.逻辑运算

str = 'aardvark'
'a' == str
1 1 0 0 0 1 0 0

%将a替换成Z
str(str == 'a') = 'Z'

5.Structure

>> student.name = 'John Doe';
>> student.id = '[email protected]';
>> student.number = 301073268;
>> student.grade = [100,74,73;95,91,85.5;100,98,72];
>> student
>
  包含以下字段的 struct:

      name: 'John Doe'
        id: '[email protected]'
    number: 301073268
     grade: [3×3 double]
>> student(2).name = 'Ann Lane';
>> student(2).id = '[email protected]';
>> student(2).number = 301078853;
>> student(2).grade = [95 100 90 ;95 82 97 ;100 85 100];
>student
>  包含以下字段的 1×2 struct 数组:

    name
    id
    number
    grade

函数	功能
cell2struct	Convent cell array to structure array
fieldnames	Field names of structure,or public fields of object
getfield	Field of structure array
isfield	Determine whether inupt is structure array field
isstruct	Determine whether input is structure array
orderfields	Order fields of structure array
rmfield	Remove fields from structure
setfield	Assign values to structure array field
struct	Create structure to cell array
struct2cell	Convert structure to cell array
structfun	Apply function to each field of scalar structure

6.Nesting structures(嵌套结构体)

>> A = struct('data',[3 4 7;8 0 1],...
              'nest',struct('testnum','Test1','xdata',[4 2 8],'ydata',[7 1 6]));
>> A(2).data = [9 3 2;7 6 5];
>> A(2).nest.testnum = 'Test 2';
>> A(2).nest.xdata = [3 4 2];
>> A(2).nest.ydata = [5 0 9];

7.Cell Array

>> A(1,1) = {[1 4 3;0 5 8;7 2 9]};
>> A(1,2) = {'Anne Smith'};
>> A(2,1) = {3 + 7i};
>> A(2,2) = {-pi:pi:pi};
>> A

A =

  2×2 cell 数组

    {3×3 double        }    {'Anne Smith'}
    {[3.0000 + 7.0000i]}    {1×3 double  }
>> A{1,1} = [1 4 3; 0 5 8;7 2 9];
>> A{1,2} = 'Anne Smith';
>> A{2,1} = 3+7i;
>> A{2,2} = -pi:pi:pi;
>> A

A =

  2×2 cell 数组

    {3×3 double        }    {'Anne Smith'}
    {[3.0000 + 7.0000i]}    {1×3 double  }

8.Accessing Cell Array 读取Cell数据

>> A(1,1)

ans =

  1×1 cell 数组

    {3×3 double}

>> A{1,1}

ans =

     1     4     3
     0     5     8
     7     2     9

函数	功能
cell	Create cell array
cell2mat	Convert cell array to numeric array
cell2struct	Convert cell array to structure array
celldisp	Cell array contents
cellfun	Apply function to each cell in cell array
cellplot	Graphically display structure of cell array
cellstr	Create cell array of strings from character array
iscell	Determine whether input is cell array
mat2cell	Convert array to cell array with different sized cells
num2cell	Convert array to cell array with consistently sized cells
struct2cell	Convert structure to cell array

>> a = magic(3)
a =
     8     1     6
     3     5     7
     4     9     2
>> b = num2cell(a)
b =
  3×3 cell 数组
    {[8]}    {[1]}    {[6]}
    {[3]}    {[5]}    {[7]}
    {[4]}    {[9]}    {[2]}
>> c = mat2cell(a,[1 1 1],3)
c =
  3×1 cell 数组
    {1×3 double}
    {1×3 double}
    {1×3 double}