clear all
clc
format compact
x=1:6
x_=norm(x,1) % 向量的1范数,元素的绝对值之和
a=norm(x,2) % 向量的2范数,或norm(x)
b=norm(x,inf) % 向量的无穷范数,元素绝对值的极大值,或max(abs(x))
c=norm(x, -inf) % 向量的负无穷范数,元素绝对值的极小值即min(abs(x))
d=diag([2,7,3])
d(3)=10
e=norm(d) % 矩阵的2范数,即最大奇异值
f=norm(d,1) %矩阵的1范数,即max(sum(abs(a))),列和极大
g=norm(d,inf) % 矩阵的无穷范数,即max(sum(abs(a'))),行和极大
h=norm(d,'fro') % 矩阵的Frobenius范数,即sqrt(sum(diag(a'*a)))
x =
1 2 3 4 5 6
x_ =
21
a =
9.5394
b =
6
c =
1
d =
2 0 0
0 7 0
0 0 3
d =
2 0 0
0 7 0
10 0 3
e =
10.6151
f =
12
g =
13
h =
12.7279
>>
矩阵的线性无关的列向量的个数:列秩
矩阵的线性无关的行向量的个数:行秩
clear all
clc
format compact
a=[2 4 5;7 9 13;3 14 5]
b=magic(3)
c=[1,2,4;3,7,10]
d=[rank(a) rank(b) rank(c)]
a =
2 4 5
7 9 13
3 14 5
b =
8 1 6
3 5 7
4 9 2
c =
1 2 4
3 7 10
d =
3 3 2
>>
a=[2 4 5;7 9 13;3 14 5]
b=magic(3)
c=[1,2,4;3,7,10;34 2 5]
d=[det(a) det(b) det(c)]
disp(['a的行列式值:', num2str(d(1))])
disp(['b的行列式值:', num2str(d(2))])
disp(['c的行列式值:', num2str(d(3))])
a =
2 4 5
7 9 13
3 14 5
b =
8 1 6
3 5 7
4 9 2
c =
1 2 4
3 7 10
34 2 5
d =
97.0000 -360.0000 -263.0000
a的行列式值:97
b的行列式值:-360
c的行列式值:-263
>>
矩阵对角元素之和。
a=[2 4 5;7 9 13;3 14 5]
b=magic(3)
c=[1,2,4;3,7,10;34 2 5]
d=[trace(a) trace(b) trace(c)]
disp(['a的迹:', num2str(d(1))])
disp(['b的迹:', num2str(d(2))])
disp(['c的迹:', num2str(d(3))])
a =
2 4 5
7 9 13
3 14 5
b =
8 1 6
3 5 7
4 9 2
c =
1 2 4
3 7 10
34 2 5
d =
16 15 13
a的迹:16
b的迹:15
c的迹:13
>>
对于非满秩矩阵A,若存在矩阵B使 A ∗ B = 0 A*B=0 A∗B=0,且 B ∗ B = I B*B=I B∗B=I,即不等于0,则称矩阵B为矩阵A的化零矩阵
a=[1,2,3;3,4,5;7 8 9]
b=null(a)
c=a*b
d=null(a,'r') % 返回有理数形式的化零矩阵
e=a*d
a =
1 2 3
3 4 5
7 8 9
b =
0.4082
-0.8165
0.4082
c =
1.0e-15 *
0.5551
-0.1110
-0.9992
d =
1
-2
1
e =
0
0
0
>>
a=[1,2,3;3,4,5;7 8 9]
q=orth(a)
b=q'*q
c=rank(a)==rank(q)
a =
1 2 3
3 4 5
7 8 9
q =
-0.2262 -0.8143
-0.4404 -0.4040
-0.8688 0.4168
b =
1.0000 -0.0000
-0.0000 1.0000
c =
logical
1
>>
a=[1,2,3;3,4,5;7 8 9]
[R,jb]=rref(a) % R是约化行阶梯形式,jb是1*r的向量,r是a的秩
b=a(:,jb) % a的列矢量构成的线性空间
a =
1 2 3
3 4 5
7 8 9
R =
1 0 -1
0 1 2
0 0 0
jb =
1 2
b =
1 2
3 4
7 8
>>
代表两个矩阵线性相关的程度,夹角越小越相关,用subspace()函数求两个矩阵的夹角
a=[1,2,3;3,4,5;7 8 9]
b=magic(3) % a,b必须同维
c=subspace(a,b)
a =
1 2 3
3 4 5
7 8 9
b =
8 1 6
3 5 7
4 9 2
c =
6.4765e-16
>>