基本操作与矩阵运算

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加减乘除优先级：

  • ^(幂) > *, / > + -

练习：

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MATLAB Calling Priority

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Numeric Display Format

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>> format short
>> pi

ans =

    3.1416

>> format long
>> pi

ans =

   3.141592653589793

>> format shortE
>> pi

ans =

   3.1416e+00

>> format longE
>> pi

ans =

     3.141592653589793e+00

>> format bank
>> pi

ans =

          3.14

>> format hex
>> pi

ans =

   400921fb54442d18

>> format rat
>> pi

ans =

     355/113

Command Line Terminal

  • 方向键向上（PgUp）可以展示上一条指令

  • clc: clear command window display

  • clear: remove all variables in the workspace

  • who: variables in the workspace

  • whos: variable information of the workspace

Array(Vector and Matrix)

  • Row vector:

a = [1 2 3 4]

  • Column vector:

b = [1;2;3;4]

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>> a = [1 2 3 4]

a =

     1     2     3     4

>> b = [1; 2; 3; 4]

b =

     1
     2
     3
     4

>> a * b

ans =

    30

>> b * a

ans =

     1     2     3     4
     2     4     6     8
     3     6     9    12
     4     8    12    16

>>

Array Indexing

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>> A = [1 21 6; 5 17 9; 31 2 7]

A =

     1    21     6
     5    17     9
    31     2     7

>> A(8)

ans =

     9

>> A(2)

ans =

     5

>> A([1 3 5])

ans =

     1    31    17

>> A([1 3; 1 3])

ans =

     1    31
     1    31

>> A(3, 2)

ans =

     2

>> A([1 3],[1 3])

ans =

     1     6
    31     7

>> A([1 2 3],[1 3])

ans =

     1     6
     5     9
    31     7

>>

Colon operator

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>> B = 1 : 5

B =

     1     2     3     4     5

>> B = 1:2:5

B =

     1     3     5

>> B = [1:5; 2:3:15; -2:0.5:0]

B =

    1.0000    2.0000    3.0000    4.0000    5.0000
    2.0000    5.0000    8.0000   11.0000   14.0000
   -2.0000   -1.5000   -1.0000   -0.5000         0

>> str = 'a':2:'z'

str =

    'acegikmoqsuwy'
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>> A = [1 21 6; 5 17 9; 31 2 7]

A =

     1    21     6
     5    17     9
    31     2     7

>> A[3, :] = []
 A[3, :] = []
  ↑
错误: 表达式无效。调用函数或对变量进行索引时，请使用圆括号。否则，请检查不匹配的分隔符。
 
>> A(3,:) = []

A =

     1    21     6
     5    17     9

>>

Array Concatenation

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>> A = [1 2; 3 4]

A =

     1     2
     3     4

>> B = [9 9; 9 9]

B =

     9     9
     9     9

>> C = [5 6 7 8]

C =

     5     6     7     8

>> D = [-2:1]

D =

    -2    -1     0     1

>> F = [A ,B; C ; D]

F =

     1     2     9     9
     3     4     9     9
     5     6     7     8
    -2    -1     0     1

>>

Array Manipulation

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>> A = [1:3; 4 5 4; 9 8 7]

A =

     1     2     3
     4     5     4
     9     8     7

>> B = [3 3 3 ;2 4 9; 1 3 1]

B =

     3     3     3
     2     4     9
     1     3     1

>> a = 2

a =

     2

>> A+a

ans =

     3     4     5
     6     7     6
    11    10     9

>> A/a

ans =

    0.5000    1.0000    1.5000
    2.0000    2.5000    2.0000
    4.5000    4.0000    3.5000

>> A./a

ans =

    0.5000    1.0000    1.5000
    2.0000    2.5000    2.0000
    4.5000    4.0000    3.5000

>> A^a

ans =

    36    36    32
    60    65    60
   104   114   108

>> A.^a

ans =

     1     4     9
    16    25    16
    81    64    49

>> A'

ans =

     1     4     9
     2     5     8
     3     4     7

>> A+B

ans =

     4     5     6
     6     9    13
    10    11     8

>> A*B

ans =

    10    20    24
    26    44    61
    50    80   106

>> A.*B

ans =

     3     6     9
     8    20    36
     9    24     7

>> A/B

ans =

    0.0714    0.2857    0.2143
    1.1667         0    0.5000
    3.2619   -0.2857   -0.2143

>> A./B

ans =

    0.3333    0.6667    1.0000
    2.0000    1.2500    0.4444
    9.0000    2.6667    7.0000

>>

Some Special Matrix

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>> linspace(0, 13, 6)

ans =

         0    2.6000    5.2000    7.8000   10.4000   13.0000

>> eye(3)

ans =

     1     0     0
     0     1     0
     0     0     1

>> zeros(2,3)

ans =

     0     0     0
     0     0     0

>> ones(2,3)

ans =

     1     1     1
     1     1     1

>> diag([2 3 4])

ans =

     2     0     0
     0     3     0
     0     0     4

>> rand(5)

ans =

    0.8147    0.0975    0.1576    0.1419    0.6557
    0.9058    0.2785    0.9706    0.4218    0.0357
    0.1270    0.5469    0.9572    0.9157    0.8491
    0.9134    0.9575    0.4854    0.7922    0.9340
    0.6324    0.9649    0.8003    0.9595    0.6787

>>

Some Matrix Related Function

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>> A = [1 2 3 ; 0 5  6; 7 0 9]

A =

     1     2     3
     0     5     6
     7     0     9

>> max(A)

ans =

     7     5     9

>> max(max(A))

ans =

     9

>> sort(A)

ans =

     0     0     3
     1     2     6
     7     5     9

>> sortrows(A)

ans =

     0     5     6
     1     2     3
     7     0     9

>> min(A)

ans =

     0     0     3

>> size(A)

ans =

     3     3

>> sum(A)

ans =

     8     7    18

>> length(A)

ans =

     3

>> mean(A)

ans =

    2.6667    2.3333    6.0000

>> find(A)

ans =

     1
     3
     4
     5
     7
     8
     9

>>
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