how to change a 3D array to a 2D array 三维数组如何转换成想要的二维数组

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收藏 2014-10-05

a<- structure(c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24),
      .Dim=c(2,4,3))
> a
, , 1

   [,1] [,2] [,3] [,4]
[1,] 1 3 5 7
[2,] 2 4 6 8

, , 2

   [,1] [,2] [,3] [,4]
[1,] 9 11 13 15
[2,] 10 12 14 16

, , 3

   [,1] [,2] [,3] [,4]
[1,] 17 19 21 23
[2,] 18 20 22 24
转换成一个3*8维的矩阵，第一行是1,9,17第二行是2,10,18，第三行行是3,11,19。。。这样共有8个列。
求简单的转换命令！

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懵兙懂少年的梦

2014-10-5 09:34:24

我也进来看看哈

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李骥北

2014-10-5 10:49:28

只想到写循环把他做出来。。

a<- structure(c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24),
            +             .Dim=c(2,4,3))

b=NULL

for (i in 1:4)
  {
  for ( j in 1:2)
{
b=cbind(b,a[j,i,])
}
}

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童小军

2014-10-6 08:34:35

李骥北发表于 2014-10-5 10:49
只想到写循环把他做出来。。

a

恩.循环肯定是可以做到的。不过自己也想到了其它更简单的命令。
> a<- structure(c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24),
+          .Dim=c(2,4,3))
> a
, , 1

   [,1] [,2] [,3] [,4]
[1,] 1 3 5 7
[2,] 2 4 6 8

, , 2

   [,1] [,2] [,3] [,4]
[1,] 9 11 13 15
[2,] 10 12 14 16

, , 3

   [,1] [,2] [,3] [,4]
[1,] 17 19 21 23
[2,] 18 20 22 24

> b=aperm(a,c(3,1,2))
> b
, , 1

   [,1] [,2]
[1,] 1 2
[2,] 9 10
[3,] 17 18

, , 2

   [,1] [,2]
[1,] 3 4
[2,] 11 12
[3,] 19 20

, , 3

   [,1] [,2]
[1,] 5 6
[2,] 13 14
[3,] 21 22

, , 4

   [,1] [,2]
[1,] 7 8
[2,] 15 16
[3,] 23 24

> c<-array(a,dim=c(3,8))
> c
   [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
[1,] 1 4 7 10 13 16 19 22
[2,] 2 5 8 11 14 17 20 23
[3,] 3 6 9 12 15 18 21 24