# combos

From quantreg v5.54
by Roger Koenker

##### Ordered Combinations

All m combinations of the first n integers taken p at a time
are computed and return as an p by m matrix. The columns
of the matrix are ordered so that adjacent columns differ
by only one element. This is just a reordered version of
`combn`

in base R, but the ordering is useful for some
applications.

- Keywords
- utilities

##### Usage

`combos(n,p)`

##### Arguments

- n
The n in n choose p

- p
The p in n choose p

##### Value

a `matrix`

of dimension p by `choose(n,p)`

##### Note

Implementation based on a Pascal algorithm of Limin Xiang
and Kazuo Ushijima (2001) translated to ratfor for R.
If you have rgl installed you might try `demo("combos")`

for a visual impression of how this works.

##### References

Limin Xiang and Kazuo Ushijima (2001)
"On O(1) Time Algorithms for Combinatorial Generation,"
*Computer Journal*, 44(4), 292-302.

##### Examples

```
# NOT RUN {
H <- combos(20,3)
# }
```

*Documentation reproduced from package quantreg, version 5.54, License: GPL (>= 2)*

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