Re: st: manipulate ordering of rows matrices

[Nick Cox <njcoxstata@gmail.com>]

It would help if you explained the essence of the difference. What
makes X2 sorted correctly?

Nick

On Tue, May 10, 2011 at 8:32 AM,  <r.a.nobel@umail.leidenuniv.nl> wrote:

> I'm having trouble with the following in Mata:
>
> From a large matrix X, I need a new matrix with unique values/rows. As an
> example, when I use :
>
> x1 = uniqrows(X)
>
> Then, the matrix given is:
>
> x1 = (
> 1,0,0,0,0,0,0,0\
> 1,0,0,0,1,0,0,0\
> 1,0,0,1,0,0,0,0\
> 1,0,1,0,0,0,0,0\
> 1,1,0,0,0,0,0,0\
> 1,1,0,0,1,0,0,1\
> 1,1,0,1,0,0,1,0\
> 1,1,1,0,0,1,0,0   )
>
> But what I need is:
>
> x2 = (
> 1,0,0,0,0,0,0,0\
> 1,0,1,0,0,0,0,0\
> 1,0,0,1,0,0,0,0\
> 1,0,0,0,1,0,0,0\
> 1,1,0,0,0,0,0,0\
> 1,1,1,0,0,1,0,0\
> 1,1,0,1,0,0,1,0\
> 1,1,0,0,1,0,0,1   )
>
> Of course, this can be done easily for just this matrix, but the problem is that
> I need the correct matrix as part of an estimation command (thus, the matrices
> can be different everytime, dependent on the dataset at hand), so I need a sort
> of general way to ensure the matrix  is always sorted correctly. However, I've
> not find a working strategy yet.

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