例6- 43  求矩陣的奇異值分解。
解：在命令窗口中輸入如下命令，并按Enter鍵確認。
>>  X=[7 8 9;4 5 6;1 2 3]
X =
     7     8     9
     4     5     6
     1     2     3
>> [U,S,V]=svd(X)
U =
   -0.8263    0.3879    0.4082
   -0.5206   -0.2496   -0.8165
   -0.2148   -0.8872    0.4082
S =
   16.8481         0         0
         0    1.0684         0
         0         0    0.0000
V =
   -0.4797    0.7767    0.4082
   -0.5724    0.0757   -0.8165
   -0.6651   -0.6253    0.4082
>> X=[1 2 3 ;6 5 4;7 8 9;12 11 10]
X =
     1     2     3
     6     5     4
     7     8     9
    12    11    10
>>  [U,S,V]=svd(X,0)
U =
   -0.1354   -0.5398    0.8275
   -0.3429    0.4384    0.2995
   -0.5453   -0.6268   -0.4716
   -0.7528    0.3514    0.0564
S =
   25.3444         0         0
         0    2.7676         0
         0         0    0.0000
V =
   -0.5936    0.6935   -0.4082
   -0.5772   -0.0134    0.8165
   -0.5608   -0.7203   -0.4082
>>