Count ’em

Suppose you have n objects and want to enumerate all possible unique allocations thereof among q groups, where “unique” is defined by numerical allocation only, independent of actual group membership for each object. Each group can take any size from 0 to n, contingent on the total in the other q-1 groups. I’m working on a problem where I have to do this; there might well be an available method for doing this, but one can waste a lot of time looking for such things in my experience, you typically learn a lot more when you have to solve a problem yourself. Anyway I couldn’t find one readily so I wrote this R function as a script. Feel free to use if it’s, well, useful.

```all.breaks = function(n, groups){
t1 = cbind(n - 0:n, n - n:0)
t1 = unique(t(apply(t1, 1, sort)))
test = groups - 2
if (test>0){
for (i in 1:test){
split=ncol(t1)
t2a = sapply(t1[,split], function(x) 0:x)
t2b = sapply(t1[,split], function(x) x:0)
reps = unlist(lapply(t2a, length))
t2a = unlist(t2a); t2b = unlist(t2b)
temp = t(apply(cbind(t2a,t2b), 1, sort))
t1 = apply(t1, 2, function(x) rep(x,reps))
t1 = cbind(t1[,-split], temp)
t1 = unique(t(apply(t1, 1, sort)))
} # End for()
} # End if()
t1 = t(apply(t1,1,sort, decreasing=T))
colnames(t1) = letters[1:groups]; rownames(t1) = 1:nrow(t1)
t1
} # End function
```

Example with 15 objects and 6 groups:

```> all.breaks(n=15, groups=6)

a b c d e f
1   15 0 0 0 0 0
2   14 1 0 0 0 0
3   13 2 0 0 0 0
4   12 3 0 0 0 0
5   11 4 0 0 0 0
6   10 5 0 0 0 0
7    9 6 0 0 0 0
8    8 7 0 0 0 0
9   13 1 1 0 0 0
10  12 2 1 0 0 0
11  11 3 1 0 0 0
12  10 4 1 0 0 0
13   9 5 1 0 0 0
14   8 6 1 0 0 0
15   7 7 1 0 0 0
16  11 2 2 0 0 0
17  10 3 2 0 0 0
18   9 4 2 0 0 0
19   8 5 2 0 0 0
20   7 6 2 0 0 0
21   9 3 3 0 0 0
22   8 4 3 0 0 0
23   7 5 3 0 0 0
24   6 6 3 0 0 0
25   7 4 4 0 0 0
26   6 5 4 0 0 0
27   5 5 5 0 0 0
28  12 1 1 1 0 0
29  11 2 1 1 0 0
30  10 3 1 1 0 0
31   9 4 1 1 0 0
32   8 5 1 1 0 0
33   7 6 1 1 0 0
34  10 2 2 1 0 0
35   9 3 2 1 0 0
36   8 4 2 1 0 0
37   7 5 2 1 0 0
38   6 6 2 1 0 0
39   8 3 3 1 0 0
40   7 4 3 1 0 0
41   6 5 3 1 0 0
42   6 4 4 1 0 0
43   5 5 4 1 0 0
44   9 2 2 2 0 0
45   8 3 2 2 0 0
46   7 4 2 2 0 0
47   6 5 2 2 0 0
48   7 3 3 2 0 0
49   6 4 3 2 0 0
50   5 5 3 2 0 0
51   5 4 4 2 0 0
52   6 3 3 3 0 0
53   5 4 3 3 0 0
54   4 4 4 3 0 0
55  11 1 1 1 1 0
56  10 2 1 1 1 0
57   9 3 1 1 1 0
58   8 4 1 1 1 0
59   7 5 1 1 1 0
60   6 6 1 1 1 0
61   9 2 2 1 1 0
62   8 3 2 1 1 0
63   7 4 2 1 1 0
64   6 5 2 1 1 0
65   7 3 3 1 1 0
66   6 4 3 1 1 0
67   5 5 3 1 1 0
68   5 4 4 1 1 0
69   8 2 2 2 1 0
70   7 3 2 2 1 0
71   6 4 2 2 1 0
72   5 5 2 2 1 0
73   6 3 3 2 1 0
74   5 4 3 2 1 0
75   4 4 4 2 1 0
76   5 3 3 3 1 0
77   4 4 3 3 1 0
78   7 2 2 2 2 0
79   6 3 2 2 2 0
80   5 4 2 2 2 0
81   5 3 3 2 2 0
82   4 4 3 2 2 0
83   4 3 3 3 2 0
84   3 3 3 3 3 0
85  10 1 1 1 1 1
86   9 2 1 1 1 1
87   8 3 1 1 1 1
88   7 4 1 1 1 1
89   6 5 1 1 1 1
90   8 2 2 1 1 1
91   7 3 2 1 1 1
92   6 4 2 1 1 1
93   5 5 2 1 1 1
94   6 3 3 1 1 1
95   5 4 3 1 1 1
96   4 4 4 1 1 1
97   7 2 2 2 1 1
98   6 3 2 2 1 1
99   5 4 2 2 1 1
100  5 3 3 2 1 1
101  4 4 3 2 1 1
102  4 3 3 3 1 1
103  6 2 2 2 2 1
104  5 3 2 2 2 1
105  4 4 2 2 2 1
106  4 3 3 2 2 1
107  3 3 3 3 2 1
108  5 2 2 2 2 2
109  4 3 2 2 2 2
110  3 3 3 2 2 2
```

The next post will examine the probabilities of each such outcome.