How can do intersection and union of two vectors?

Hello everyone, I have two vector A and B :

A=[256 1 6 8 4 5 78 25];
B=[85 22 1 25 2 589 6 3];

I want to have other vector result that consist of the union or the intersection of the elements in A and B like this:

 result_union=[256,85,1,22,6,8,25,4,2,5,589,78,25,3];
 result_intersect=[1,6,25];

Please, help me how can can I do it?

Answer 1

[Stephen23]

Intersection: simply use intersect with the stable option:

>> A = [256,1,6,8,4,5,78,25];
>> B = [85,22,1,25,2,589,6,3];
>> intersect(A,B,'stable')
ans =
     1     6    25

Union: to keep the order of the two vectors (like they were zipped or interleaved together), then you could concatenate the vectors and then use unique like this:

>> unique(reshape([A;B],1,[]),'stable')
ans =
   256    85     1    22     6     8    25     4     2     5   589    78     3

If the vectors have different lengths then you could use this FEX submission to zip them together (instead of the concatenation and rehsape in my example):

http://www.mathworks.com/matlabcentral/fileexchange/16919-interleave

[Sahar abdalah]

thanks

[Titus Edelhofer]

Nice, Stephen!

Answer 2

[Titus Edelhofer]

Hi,

did you try to enter union or intersect in the documentation search? It should give you at least for the intersection a good result ;-).

Regarding the union it depends on if you require exact the ordering that you gave ...

Titus

[Sahar abdalah]

the problem when I use both union and intersect function in matlab is that I get a vector of increasing order then I want to do the union element by element as in the example without order.

 result_union= [ 1     2     3     4     5     6     8    22    25    78    85   256   589]

 result_intersect = [1     6    25]

[Titus Edelhofer]

There is an ordering parameter for intersect and union:

intersect(A,B, 'stable')

although for union is does not help (directly), since it's using the values from A first and then from B. I guess you need to work it up "by hand".

Titus