Finding pair values in a matrix

We had to calculate how many pairs we can find for the pythagorean triads for a,b,c when a^2+b^2=c^2. After we found those we had to create a matrix that included all possible pairs for a and b. For a=[1:100] and b=[1:200] I got 184 pairs. So now my matrix z is a 184x2 matrix, but there are definitely some pairs that are repeated. For example, when c=5 we get two possibilities x=3 and y=4, but also x=4 and y=3.

How can I make the code, so that if i have the rows (3,4) and (4,3), either one will be deleted and I can have a new matrix just for the possible pairs without caring which one is x or y?

I tried doing that with groupcounts(z) but that only works with vectors, not matrices. Any ideas?

[the cyclist]

Can you say exactly what the input is, and exactly what you want the output to be?

Is it just, for example, that if you have a matrix

z = [1 2;
     2 1;
     3 4;
     4 3;
     5 6;
     6 5];

that you want to return

 z2 = [1 2;
       3 4;
       5 6];

?

It would be helpful if you gave a small, specific example that has enough generality to cover what you want to do.

You can upload data in a MAT file using, the paper-clip icon.

[Christina Petsa]

That is exactly what I meant. Sorry for not specifying enough!

Answer 1

[Tommy]

How about this?

z = unique(sort(z,2),'rows');

[the cyclist]

I shouldn't have spent 6 minutes composing my lengthy comment and then answer. :-)

[Christina Petsa]

Thank you!

[Christina Petsa]

It doesn't work the way we expected. If you don't mind I replied what the output is bellow, if you have any more ideas, I'd be thankful!

Answer 2

[the cyclist]

If my speculation in the comment above about what you want for z2 is correct, then

z2 = unique(sort(z,2),'row')

[Christina Petsa]

Thank you for your input!

[Christina Petsa]

Hey, I just tried that but the result I get when I type that is two collumns of the same values.

I wanted what you explained above; if z=[3 4; 4 3; 5 2; 2 5] , i want to create a new one that is z2=[3 4; 5 2]

However with this I get a matrix that shows z2=[3 3; 4 4; 5 5;......] etc

Thanks in advance if you have any more ideas...

[the cyclist]

Are you absolutely certain you typed the solution code exactly as we wrote it? Because it worked for me.

I'm guessing maybe you wrote

sort(z)

instead of

sort(z,2)

The correct syntax sorts along dimension 2.