# reshape

Reshape symbolic array

## Description

`reshape(`

lets
you represent a size value with the placeholder `A`

,...,[],...)`[]`

while
calculating the magnitude of that size value automatically. For example,
if `A`

has size 2-by-6, then `reshape(A,4,[])`

returns
a 4-by-3 array.

## Examples

### Reshape Symbolic Row Vector into Column Vector

Reshape `V`

, which is a 1-by-4 row vector, into the 4-by-1
column vector `Y`

. Here, `V`

and `Y`

must have the same number of elements.

Create the vector `V`

.

syms f(x) y V = [3 f(x) -4 y]

V = [ 3, f(x), -4, y]

Reshape `V`

into `Y`

.

Y = reshape(V,4,1)

Y = 3 f(x) -4 y

Alternatively, use `Y = V.'`

where `.'`

is
the nonconjugate transpose.

### Reshape Symbolic Matrix

Reshape the 2-by-6 symbolic matrix `M`

into
a 4-by-3 matrix.

M = sym([1 9 4 3 0 1; 3 9 5 1 9 2]) N = reshape(M,4,3)

M = [ 1, 9, 4, 3, 0, 1] [ 3, 9, 5, 1, 9, 2] N = [ 1, 4, 0] [ 3, 5, 9] [ 9, 3, 1] [ 9, 1, 2]

`M`

and `N`

must have the
same number of elements. `reshape`

reads `M`

column-wise
to fill in the elements of `N`

column-wise.

Alternatively, use a size vector to specify the dimensions of the reshaped matrix.

sz = [4 3]; N = reshape(M,sz)

N = [ 1, 4, 0] [ 3, 5, 9] [ 9, 3, 1] [ 9, 1, 2]

### Automatically Set Dimension of Reshaped Matrix

When you replace a dimension with the placeholder `[]`

, `reshape`

calculates
the required magnitude of that dimension to reshape the matrix.

Create the matrix `M`

.

M = sym([1 9 4 3 0 1; 3 9 5 1 9 2])

M = [ 1, 9, 4, 3, 0, 1] [ 3, 9, 5, 1, 9, 2]

Reshape `M`

into a matrix with three columns.

reshape(M,[],3)

ans = [ 1, 4, 0] [ 3, 5, 9] [ 9, 3, 1] [ 9, 1, 2]

`reshape`

calculates that a reshaped matrix
of three columns needs four rows.

### Reshape Matrix Row-wise

Reshape a matrix row-wise by transposing the result.

Create matrix `M`

.

syms x M = sym([1 9 0 sin(x) 2 2; NaN x 5 1 4 7])

M = [ 1, 9, 0, sin(x), 2, 2] [ NaN, x, 5, 1, 4, 7]

Reshape `M`

row-wise by transposing the result.

reshape(M,4,3).'

ans = [ 1, NaN, 9, x] [ 0, 5, sin(x), 1] [ 2, 4, 2, 7]

Note that `.'`

returns the non-conjugate transpose
while `'`

returns the conjugate transpose.

### Reshape 3-D Array into 2-D Matrix

Reshape the 3-by-3-by-2 array `M`

into
a 9-by-2 matrix.

`M`

has 18 elements. Because a 9-by-2 matrix
also has 18 elements, `M`

can be reshaped into it.
Construct `M`

.

syms x M = [sin(x) x 4; 3 2 9; 8 x x]; M(:,:,2) = M'

M(:,:,1) = [ sin(x), x, 4] [ 3, 2, 9] [ 8, x, x] M(:,:,2) = [ sin(conj(x)), 3, 8] [ conj(x), 2, conj(x)] [ 4, 9, conj(x)]

Reshape `M`

into a 9-by-2 matrix.

N = reshape(M,9,2)

N = [ sin(x), sin(conj(x))] [ 3, conj(x)] [ 8, 4] [ x, 3] [ 2, 2] [ x, 9] [ 4, 8] [ 9, conj(x)] [ x, conj(x)]

### Use reshape to Break Up Arrays

Use `reshape`

instead of loops
to break up arrays for further computation. Use `reshape`

to
break up the vector `V`

to find the product of every
three elements.

Create vector `V`

.

syms x V = [exp(x) 1 3 9 x 2 7 7 1 8 x^2 3 4 sin(x) x]

V = [ exp(x), 1, 3, 9, x, 2, 7, 7, 1, 8, x^2, 3, 4, sin(x), x]

Specify `3`

for the number of rows. Use the
placeholder `[]`

for the number of columns. This
lets `reshape`

automatically calculate the number
of columns required for three rows.

M = prod( reshape(V,3,[]) )

M = [ 3*exp(x), 18*x, 49, 24*x^2, 4*x*sin(x)]

`reshape`

calculates that five columns are
required for a matrix of three rows. `prod`

then
multiples the elements of each column to return the result.

## Input Arguments

## Version History

**Introduced before R2006a**