[Gretl-users] reversing / flipping a matrix

Riccardo (Jack) Lucchetti r.lucchetti at univpm.it
Fri Jul 10 06:00:57 EDT 2009


On Fri, 10 Jul 2009, Riccardo (Jack) Lucchetti wrote:

> On Fri, 10 Jul 2009, Sven Schreiber wrote:
>
>> Dear gretl users,
>> 
>> yesterday I needed to flip a matrix/vector around by reversing the order
>> of the elements. (I guess like rev() or flipud() in other languages.)
>> But I didn't find the function to do that, so I used an inefficient
>> workaround using msortby(). But since this seems like quite basic
>> functionality I think I either missed something or it should be added,
>> right?
>
> Right. I must have said to myself "I need to do this. Oh well, not now" a 
> thousand times. It's now in CVS. The user-level function is called rev(). 
> Example:
>
> ? A = rev(I(3))
> A = rev(I(3))
> Generated matrix A
> ? print A
> print A
> A (3 x 3)
>
>  0   0   1
>  0   1   0
>  1   0   0

Oh, sorry, I should have said: the rev() function reverses the order of 
the _rows_ of the matrix (from the example above, it could have been the 
columns).

Riccardo (Jack) Lucchetti
Dipartimento di Economia
Università Politecnica delle Marche

r.lucchetti at univpm.it
http://www.econ.univpm.it/lucchetti


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