Find common data between two vectors

I have two vectors A and B they both are different length, but a good portion of the values are common to both.

A = [3 4 6 1 7 2 5 6 7 9 0 3 2 8];
B = [4 5 6 6 1 7 2 5 6 7 9 0 3 2 0 5 8 7];

I need to find the indices where [6 1 7 2 5 6 7 9 0 3 2] begin and end

ia = [3 13];
ib = [4 14]

[Walter Roberson]

Are you looking for the beginning and ending indices of the largest consecutive common sequence ?

[hegel]

yes

Answer 1

[John D'Errico]

If you are looking for the longest common substring?

Assuming the elements of A and B are integers, then use of my commonsubstring utility works:

A = [3 4 6 1 7 2 5 6 7 9 0 3 2 8];
B = [4 5 6 6 1 7 2 5 6 7 9 0 3 2 0 5 8 7];
[S,ind1,ind2] = commonsubstring(char(A),char(B))
S =
    '   '
ind1 =
  1×1 cell array
    {[3]}
ind2 =
  1×1 cell array
    {[4]}

+S
ans =
     6     1     7     2     5     6     7     9     0     3     2

So the common substring begins at element 3 of A, element 4 of B.

The length of the string is

numel(S)
ans =
    11

So that gives you the end points in each string.

A = randi(9,1,10000);
B = randi(9,1,2000);

[S,ind1,ind2] = commonsubstring(char(A),char(B))
S =
    '  '
ind1 =
  1×1 cell array
    {[691]}
ind2 =
  1×1 cell array
    {[756]}

+S
ans =
     5     4     4     2     3     1     9     6

It can be found here:

https://www.mathworks.com/matlabcentral/fileexchange/27460-string-subsequence-tools

[hegel]

Thank you!

Answer 2

[Birdman]

One approach:

A = [3 4 6 1 7 2 5 6 7 9 0 3 2 8];
B = [4 5 6 6 1 7 2 5 6 7 9 0 3 2 0 5 8 7];
pattern = [6 1 7 2 5 6 7 9 0 3 2];
[ia1,ia2]=regexp(reshape(char(string(A)),1,[]),reshape(char(string(pattern)),1,[]));
[ib1,ib2]=regexp(reshape(char(string(B)),1,[]),reshape(char(string(pattern)),1,[]));
ia=[ia1 ia2]
ib=[ib1 ib2]

[hegel]

Thank you!

Answer 3

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/24559-longest-common-subsequence

https://www.mathworks.com/matlabcentral/fileexchange/27460-string-subsequence-tools

[hegel]

Thank you!