reshape把指定的矩阵改变形状，但是元素个数不变，

例如，行向量：

a = [1 2 3 4 5 6]

执行下面语句把它变成3行2列：

b = reshape(a,3,2)

执行结果：

b =

1 4

2 5

3 6

若a=[1 2 3

4 5 6

7 8 9]

可以从b中看到reshape是按列来读取的，如

a=[1  2 ; 3  4]

如果使用b=reshape(a,1,4)

则得到的结果是

b=[1 3 2 4]

如果想得到

b=[1 2 3 4]

需要使用

b=reshape(a\',1,4)

因为reshape使用的列优先！

b转化回去是同样的道理。

使用reshpe后想得到b=[1 2 3 4 5 6 7 8 9]

只需要将a转置一下就可以了：

b=reshape(a\',1,9)

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matlab中的解释如下：

RESHAPE Change size.

    RESHAPE(X,M,N) returns the M-by-N matrix whose elements

    are taken columnwise from X. An error results if X does

    not have M*N elements.

    RESHAPE(X,M,N,P,...) returns an N-D array with the same

    elements as X but reshaped to have the size M-by-N-by-P-by-...

    M*N*P*... must be the same as PROD(SIZE(X)).

    RESHAPE(X,[M N P ...]) is the same thing.

    RESHAPE(X,...,[],...) calculates the length of the dimension

    represented by [], such that the product of the dimensions

    equals PROD(SIZE(X)). PROD(SIZE(X)) must be evenly divisible

    by the product of the known dimensions. You can use only one

    occurrence of [].

    In general, RESHAPE(X,SIZ) returns an N-D array with the same

    elements as X but reshaped to the size SIZ. PROD(SIZ) must be

    the same as PROD(SIZE(X)).

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