compare matrix elements

[gkiom]

Hi all. I'm new in matlab and i want to do smth like that:

Having two matrixes(vectors is better), like

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

I want to compare all elements of A to B, and if an element of A is same with one of B (not in same position necessarilly) to be written in another vector. In this example, i want to create a vector like

C=[6;5]

I spent many hours reading help documentation on matrixes but to no avail. I found smth like 'any' but did not understand it's functionality, and especially if it feets my needs.

Is this ....SO difficult...? I do not suppose so, but is there anyone here available to show me how?

Thanx in advance.

 

[sirmarhalt]

Hi, the first thing I think to is to use for loops to control all position in both matrices.

[ra ca]=size(A);
[rb cb]=size(B);
t=1;
for i=1:ra
for j=1:ca
for k=1:rb
for l=1:cb
if A(i,j)==B(k,l)
C(t)=A(i,j);
t=t+1;
end;
end;
end;
end;
end;

There is another way, using function 'find':
[ra ca]=size(A);
[rb cb]=size(B);
t=1;
for i=1:ra
for j=1:ca
if isempty(find(B==A(i,j)))==0
C(t)=A(i,j);
t=t+1;
end;
end;
end;

Function find returns every value and index sattisfies the condition between brackets. If condition is not satisfied returns empty value. 'isempty' returns 1 if inside its brackets there is empty value.
I don't know which one is faster, because I think that behind function find there are for loops (and mabye for loops will be more direct). Only in case you work with larger matrixs.

Good luck

 

[MikeyP]

Jeez, that has to be a record for the greatest number of redundant "for" loops!

What is wrong with this

A=[1;2;6;3;5;8]
B=[4;6;9;7;4;5]
C=intersect(A,B)

M

--
Dr Michael F Platten

 

[gkiom]

Thank you both. I will check for "help intersect" on the command window first and try some of the "for" loops as well, just to get acquainted with them. Thank you both ppl.

 

[SomptingGuy]

If A and B are the same length (and not too long!), this obfuscated one-liner will also work. I'm not suggesting it's a good solution, but one that'll teach you a thing or two about Matlab.

B(sum(perms(A)==B,ones(1,factorial(length(A))))')>0)

 

[gkiom]

B(sum(perms(A)==B,ones(1,factorial(length(A))))')>0)

At this point, the only thing i understand in the line above, is 'sum' (lol). It seems that i have to do a lot of reading!

Oh, i can also understand 'length'

(grateful)