I have a dataset like this:

```
    case x y 
      1  4 5  
      2  4 5  
      3  8 9 
      4  7 9
      5  6 3
      6  6 3

```

I would like to create a grouping variable. 
This variable should have the same values when both x and y are the same. 
I do not care what this value is but it is to group them. Because in my dataset if x and y are the same for two cases they are probably part of the same organization. I want to see which organizations there are.

So my preferred dataset would look like this:

```
    case x y org
      1  4 5  1
      2  4 5  1
      3  8 9  2
      4  7 9  3
      5  6 3  4 
      6  6 3  4

```

How would I have to program this in R?