`shiftdim`

Shifts the dimensions of an array, removing or adding leading singleton dimensions.

Category: Language Fundamentals > Matrices and Arrays

Syntax

B = shiftdim(A)

Removes leading singleton dimensions.

B = shiftdim(A, n)

Shifts dimensions left by n (cyclically); a negative n adds -n leading singletons.

[B, ns] = shiftdim(A)

Also returns the number of dimensions removed.

Description

A common case is an array of size 1-by-1-by-k, produced by slicing a 3-D array; shiftdim turns it into a plain k-by-1 vector. With a positive n the first n dimensions move to the end, so an array of size [2 3 4] shifted by 1 has size [3 4 2]. This is the same as a permute by a rotated order.

Input arguments

A: Array of any type.
n: Number of positions to shift; integer.

Output arguments

B: Array with the same elements and shifted dimensions.
ns: Number of leading singleton dimensions that were removed.

Example

x = ones(1, 1, 3);
size(shiftdim(x))
size(shiftdim(ones(2, 3, 4), 1))
size(shiftdim(ones(2, 3), -1))

Output

ans = 1×2

     3     1
ans = 1×3

     3     4     2
ans = 1×3

     1     2     3

shiftdim