reshape
Reshape array by rearranging existing elements
Description
reshapes B
= reshape(A
,sz1,...,szN
)A
into
a sz1
-by-...
-by-szN
array
where sz1,...,szN
indicates the size of each dimension.
You can specify a single dimension size of []
to
have the dimension size automatically calculated, such that the number
of elements in B
matches the number of elements
in A
. For example, if A
is a
10-by-10 matrix, then reshape(A,2,2,[])
reshapes
the 100 elements of A
into a 2-by-2-by-25 array.
Examples
Reshape Vector into Matrix
Reshape a 1-by-10 vector into a 5-by-2 matrix.
A = 1:10; B = reshape(A,[5,2])
B = 5×2
1 6
2 7
3 8
4 9
5 10
Reshape Matrix to Have Specified Number of Columns
Reshape a 4-by-4 square matrix into a matrix that has 2 columns. Specify []
for the first dimension to let reshape
automatically calculate the appropriate number of rows.
A = magic(4)
A = 4×4
16 2 3 13
5 11 10 8
9 7 6 12
4 14 15 1
B = reshape(A,[],2)
B = 8×2
16 3
5 10
9 6
4 15
2 13
11 8
7 12
14 1
The result is an 8-by-2 matrix, which maintains the same number of elements as the original matrix. The elements in B
also maintain their columnwise order from A
.
Reshape Multidimensional Array into Matrix
Reshape a 2-by-2-by-3 array of random values into a 6-by-2 matrix.
rng default
A = rand(2,2,3)
A = A(:,:,1) = 0.8147 0.1270 0.9058 0.9134 A(:,:,2) = 0.6324 0.2785 0.0975 0.5469 A(:,:,3) = 0.9575 0.1576 0.9649 0.9706
B = reshape(A,6,2)
B = 6×2
0.8147 0.2785
0.9058 0.5469
0.1270 0.9575
0.9134 0.9649
0.6324 0.1576
0.0975 0.9706
Input Arguments
A
— Input array
vector | matrix | multidimensional array
Input array, specified as a vector, matrix, or multidimensional array.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| logical
| char
| string
| cell
| struct
| datetime
| duration
| calendarDuration
Complex Number Support: Yes
sz
— Output size
row vector of integers
Output size, specified as a row vector of integers. Each element
of sz
indicates the size of the corresponding dimension
in B
. You must specify sz
so
that the number of elements in A
and B
are
the same. That is, prod(sz)
must be the same as numel(A)
.
Beyond the second dimension, the output, B
,
does not reflect trailing dimensions with a size of 1
.
For example, reshape(A,[3,2,1,1])
produces a 3-by-2
matrix.
Example: reshape(A,[3,2])
Example: reshape(A,[6,4,10])
Example: reshape(A,[5,5,5,5])
sz1,...,szN
— Size of each dimension
two or more integers | []
(optional)
Size of each dimension, specified as two or more integers with
at most one []
(optional). You must specify at
least 2 dimension sizes, and at most one dimension size can be specified
as []
, which automatically calculates the size
of that dimension to ensure that numel(B)
matches numel(A)
.
When you use []
to automatically calculate a dimension
size, the dimensions that you do explicitly specify
must divide evenly into the number of elements in the input matrix, numel(A)
.
Beyond the second dimension, the output, B
,
does not reflect trailing dimensions with a size of 1
.
For example, reshape(A,3,2,1,1)
produces a 3-by-2
matrix.
Example: reshape(A,3,2)
Example: reshape(A,6,[],10)
Example: reshape(A,2,5,3,[])
Example: reshape(A,5,5,5,5)
Output Arguments
B
— Reshaped array
vector | matrix | multidimensional array | cell array
Reshaped array, returned as a vector, matrix, multidimensional
array, or cell array. The data type and number of elements in B
are
the same as the data type and number of elements in A
.
The elements in B
preserve their columnwise ordering
from A
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| logical
| char
| string
| cell
| datetime
| duration
| calendarDuration
Tips
The
reshape
function rearranges existing elements in the input data. To add or remove elements, use theresize
function.
Extended Capabilities
Tall Arrays
Calculate with arrays that have more rows than fit in memory.
This function supports tall arrays with the limitations:
Reshaping the tall dimension (dimension one) is not supported. The first dimension input should always be empty, such as
reshape(X,[],M,N,...)
.
For more information, see Tall Arrays for Out-of-Memory Data.
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
If the input is a compile-time empty cell array, then the size arguments must be constants.
Size arguments must have a fixed size.
See Variable-Sizing Restrictions for Code Generation of Toolbox Functions (MATLAB Coder).
For sparse matrices, the
reshape
function does not support trailing ones as inputs after the first two dimensions.
GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.
Usage notes and limitations:
If the input is a compile-time empty cell array, then the size arguments must be constants.
Size arguments must have a fixed size.
For sparse matrices, the
reshape
function does not support trailing ones as inputs after the first two dimensions.
HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.
Thread-Based Environment
Run code in the background using MATLAB® backgroundPool
or accelerate code with Parallel Computing Toolbox™ ThreadPool
.
This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.
GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.
The reshape
function
supports GPU array input with these usage notes and limitations:
Input array
A
must be nonsparse.
For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).
Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.
This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).
Version History
Introduced before R2006a
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