# Re: [R] Help to make a specific matrix

Date: Sun 10 Jul 2005 - 22:36:37 EST

In addition to Gabor's solution, you might be interested in the combinations function from the gtools package.

library(gtools)
combinations(5,2)

[,1] [,2]

``` [1,]    1    2
[2,]    1    3
[3,]    1    4
[4,]    1    5
[5,]    2    3
[6,]    2    4
[7,]    2    5
[8,]    3    4
[9,]    3    5
```

[10,] 4 5

On Sat, 2005-07-09 at 21:42 -0300, Jose Claudio Faria wrote:
> Dear R users,
>
> The solution is probably simple but I need someone to point me to it.
> How can I to generate a matrix from a numeric sequence of 1:10 like 'A' or 'B'
> below:
>
> A)
> |--------------------|
> | 1 2 3 4 5 |
> |--------------------|
> | 1 | 0 |
> | 2 | 1 0 |
> | 3 | 2 5 0 |
> | 4 | 3 6 8 0 |
> | 5 | 4 7 9 10 0 |
> |--------------------|
>
> B)
> |--------------------|
> | 1 2 3 4 5 |
> |--------------------|
> | 1 | 0 1 2 3 4 |
> | 2 | 1 0 5 6 7 |
> | 3 | 2 5 0 8 9 |
> | 4 | 3 6 8 0 10 |
> | 5 | 4 7 9 10 0 |
> |--------------------|
>
> This question is related with the possible combinations of five objects two the
> two, i.e, C(5,2).
>
> Any help would be greatly appreciated.
>
> Regards,

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