[已答复] 矩阵相除,不解。。

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doublesolitons 发表于 2011-5-17 05:35:22
>> a

a =

     0     3     3
     4    34     3
     2     3     7

>> b

b =

     2
     5
     7

>> b\a

ans =

    0.4359    2.5256    0.8974

>> inv(b)
??? Error using ==> inv
Matrix must be square.

不明的地方是,b\a应该是b^(-1)*a,而b^(-1)由于不是方阵,没有矩阵的逆,那b\a是怎么求的呢?在下新手,求大侠解惑啊~

4 条回复


doublesolitons 发表于 2011-5-27 13:47:38
顶啊,大家帮帮忙。。

moset 发表于 2011-5-27 14:35:17
为什么,不自己看帮助先呢。
"\":Backslash or matrix
left division. If A is a square matrix, AB is
roughly the same as inv(A)*B, except it is computed in
a different way. If A is an n-by-n matrix
and B is a column vector with n components,
or a matrix with several such columns, then X = AB is
the solution to the equation AX = B computed by Gaussian
elimination. A warning message is displayed if A is badly
scaled or nearly singular. See the reference page for mldivide for
more information.
  If A is an m-by-n matrix
with m ~= n and B is a column vector
with m components, or a matrix with several such columns,
then X = AB is the solution in the least squares sense
to the under- or overdetermined system of equations AX = B.
The effective rank, k, of A is determined
from the QR decomposition with pivoting (see Algorithm for details). A solution X is computed
that has at most k nonzero components per column. If k
< n, this is usually not the same solution as pinv(A)*B,
which is the least squares solution with the smallest norm
.

ymd1234 发表于 2011-5-29 18:49:47
伪逆吧。。。

MATLAB学徒 发表于 2011-5-30 11:09:39

回复 1# doublesolitons 的帖子

左除(\):相当于求解AX=B,X=A\B,这是最小二乘解;
右除(/):相当于求解XA=B,X=B/A。
一个矩阵的行列式不为零,才能求逆矩阵的。
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