permute

Rearranging dimensions

Usage

b = permute(a, order)

• a is an array.
• It rearranges the dimensions of a according to the order specified by order. The order(i)-th dimension of a is shifted to the i-th dimension in the new array b.
• It is the inverse operation of ipermute.
• order should be a permutation of the vector 1:length(order) with length(order) >= ndims(a)

Examples

• Swapping 1st and 2nd dimenions. This is the same as taking transpose of a.

Input

a = [1 2 3;4 5 6];
permute(a,[2 1])

Output

ans = 
 1.0000   4.0000
 2.0000   5.0000
 3.0000   6.0000

• In the following, order has a length larger than ndims(a). Thus, 3rd, 4th, and 5th dimensions of a are considered as singleton, i.e., having lengths of 1. The 5th dimension of b is singleton, and therefore ndims(b) is 4.

Input

a = rand(3,4);
b = permute(a,[3 1 4 2 5]);
size(b)
ndims(b)

Output

ans = 
 1.0000   3.0000   1.0000   4.0000   1.0000

ans = 
 4.0000

• permute is the inverse operation of ipermute.

Input

a = rand(3,4);
b = ipermute(a,[3 1 4 2 5]);
c = permute(b,[3 1 4 2 5]);

% a and c have the same sizes
size(a),size(c)

% a and c are the same matrices
a - c

Output

ans = 
 3.0000   4.0000

ans = 
 3.0000   4.0000   1.0000   1.0000   1.0000

ans = 
 0.0000   0.0000   0.0000   0.0000
 0.0000   0.0000   0.0000   0.0000
 0.0000   0.0000   0.0000   0.0000