>> A = [1 2; 3 4; 5 6]
A =
1 2
3 4
5 6
>> B = [11 12; 13 14; 15 16]
B =
11 12
13 14
15 16
>> C = [1 1; 2 2]
C =
1 1
2 2
>> A*C %矩阵乘法
ans =
5 5
11 11
17 17
>> A .* B %两个矩阵的对应元素相乘
ans =
11 24
39 56
75 96
>> A .^ 2 %A中的每个元素都平方
ans =
1 4
9 16
25 36
>> v = [1; 2; 3]
v =
1
2
3
>> 1 ./ v %对每一个元素求倒数
ans =
1.00000
0.50000
0.33333
>> log(v) %对每一个元素求对数
ans =
0.00000
0.69315
1.09861
>> exp(v) %以每个元素为指数，求e的幂
ans =
2.7183
7.3891
20.0855
>> abs(v) %求每个元素的绝对值
ans =
1
2
3
>> abs([-1; 2; -3])
ans =
1
2
3
>> -v % -1*v
ans =
-1
-2
-3
>> v + ones(size(v)) %给每个元素加1
ans =
2
3
4
>> ones(size(v))
ans =
1
1
1
>> v + 1
ans =
2
3
4
>> A
A =
1 2
3 4
5 6
>> A' %transpose
ans =
1 3 5
2 4 6
>> (A')'
ans =
1 2
3 4
5 6
>> a
a =
1.00000 15.00000 2.00000 0.50000
>> val = max(a)
val = 15
>> [val, ind] = max(a) %ind是最大值val的索引
val = 15
ind = 2
>>
>>
>> A
A =
1 2
3 4
5 6
>> max(A) %求每一列的最大值
ans =
5 6
>> a
a =
1.00000 15.00000 2.00000 0.50000
>> a < 3 %逐个对比
ans =
1 0 1 1
>> find(a < 3) %满足条件的索引
ans =
1 3 4
>>
>>
>> A = magic(3) %生成3X3幻方,每行每列每条对角线之和均相等
A =
8 1 6
3 5 7
4 9 2
>> [r, c] = find(A >= 7) %r是row c是column
r =
1
3
2
c =
1
2
3
>> A(r(1), c(1))
ans = 8
>> A(r(2), c(2))
ans = 9
>> A(r(3), c(3))
ans = 7
>>
>>
>> a
a =
1.00000 15.00000 2.00000 0.50000
>> sum(a) %所有元素求和
ans = 18.500
>> prod(a) %所有元素求积
ans = 15
>> floor(a) %每个元素向下取整
ans =
1 15 2 0
>> ceil(a) %每个元素向上取整
ans =
1 15 2 1
>> rand(3)
ans =
0.61469 0.18858 0.55845
0.59182 0.66372 0.79564
0.80858 0.73942 0.54067
>> max(rand(3), rand(3)) %两个矩阵中对应元素取最大值
ans =
0.71192 0.63884 0.71841
0.72794 0.89119 0.85213
0.93154 0.62869 0.21294
>> A
A =
8 1 6
3 5 7
4 9 2
>> max(A,[],1) %第3个参数是指按列取最大值，第2个参数忽略
ans =
8 9 7
>> max(A,[],2) %第3个参数是指按行取最大值，第2个参数忽略
ans =
8
7
9
>> max(A)
ans =
8 9 7
>> max(max(A))
ans = 9
>> A(:)
ans =
8
3
4
1
5
9
6
7
2
>> max(A(:))
ans = 9
>> A = magic(9)
A =
47 58 69 80 1 12 23 34 45
57 68 79 9 11 22 33 44 46
67 78 8 10 21 32 43 54 56
77 7 18 20 31 42 53 55 66
6 17 19 30 41 52 63 65 76
16 27 29 40 51 62 64 75 5
26 28 39 50 61 72 74 4 15
36 38 49 60 71 73 3 14 25
37 48 59 70 81 2 13 24 35
>> sum(A, 1) %按列求和
ans =
369 369 369 369 369 369 369 369 369
>> sum(A, 2) %按行求和
ans =
369
369
369
369
369
369
369
369
369
>> sum( sum(A .* eye(9)) ) %主对角线求和
ans = 369
>> sum( sum(A .* flipud(eye(9))) ) %副对角线求和
ans = 369
>>
>> eye(9)
ans =
Diagonal Matrix
1 0 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0
0 0 0 1 0 0 0 0 0
0 0 0 0 1 0 0 0 0
0 0 0 0 0 1 0 0 0
0 0 0 0 0 0 1 0 0
0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 0 1
>> flipud(eye(9)) %上下翻转
ans =
Permutation Matrix
0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 0 0
0 0 0 0 0 1 0 0 0
0 0 0 0 1 0 0 0 0
0 0 0 1 0 0 0 0 0
0 0 1 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 0
>> A = magic(3)
A =
8 1 6
3 5 7
4 9 2
>> Ainv = pinv(A) %求逆
Ainv =
0.147222 -0.144444 0.063889
-0.061111 0.022222 0.105556
-0.019444 0.188889 -0.102778
>> A * Ainv %A乘A逆约等于I
ans =
1.0000e+00 -1.2157e-14 6.3560e-15
5.5511e-17 1.0000e+00 -1.5266e-16
-5.9813e-15 1.2268e-14 1.0000e+00
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