Programming |
Permuting Array Dimensions
The permute
function reorders the dimensions of an array:
dims
is a vector specifying the new order for the dimensions of A
, where 1 corresponds to the first dimension (rows), 2 corresponds to the second dimension (columns), 3 corresponds to pages, and so on.
For a more detailed look at the permute
function, consider a four-dimensional array A
of size 5-by-4-by-3-by-2. Rearrange the dimensions, placing the column dimension first, followed by the second page dimension, the first page dimension, then the row dimension. The result is a 4-by-2-by-3-by-5 array.
You can think of permute
's operation as an extension of the transpose
function, which switches the row and column dimensions of a matrix. For permute
, the order of the input dimension list determines the reordering of the subscripts. In the example above, element (4,2,1,2)
of A
becomes element (2,2,1,4)
of B
, element (5,4,3,2)
of A
becomes element (4,2,3,5)
of B
, and so on.
Inverse Permutation
The ipermute
function is the inverse of permute
. Given an input array A
and a vector of dimensions v
, ipermute
produces an array B
such that permute(B,v)
returns A
.
For example, these statements create an array E
that is equal to the input array C
:
You can obtain the original array after permuting it by calling ipermute
with the same vector of dimensions.
Reshaping Multidimensional Arrays | Computing with Multidimensional Arrays |
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