FINDIND

FINDIND - find indices of matching elements between two matrices

IB = FINDIND(A,B) returns a cell array IB which has the same size as A.
Each cell of IB contains a row vector with the indices of those elements
of B that are equal to the corresponding element of A. In other words,
for each k, IB{k} equals "find(B == A(k))".

[IB, IA] = FINDIND(A,B) also return another cell array IA holding the
indices of those elements of A that are equal to the corresponding
element of B. In other words, for each k, IA{k} equals "find(A == B(k))".

A and B may have repeated elements. If an element of A or B is not
present in B or A, the corresponding cell will be empty. A and B can be
cell array of strings.

Example:
A = [1 4 2 ; 3 4 5] ;
B = [1 2 1 1 4 2 2 2 4 5 5] ;
x = findind(A,B)
% -> x = {[ 1 3 4 ], [ 5 9 ], [ 2 6 7 8 ]
% [] , [ 5 9 ], [10 11] }

See also find, ismember, unique