st: Generate data and matrix from unbalanced panel

[Marcello Pagano <pagano@hsph.harvard.edu>]

Nguyen Cong Minh wrote:
> Subject: Generate data and matrix from unbalanced panel
>
> Hi,
>
> I have the unbalanced panel data like this:
>
> Id	yr	var1	var2	var3
> 1	1991	2	3	4
> 1	1992	32	32	22
> 1	1993	32	2	23
> 2	1992	21	32	32
> 2	1993	32	49	88
> 3	1991	22	32	34
> 3	1992	32	87	76
> 3	1993	33	32	43
> 4	1991	3	44	33
> 5	1993	32	33	32
> ..	..	..	..	..
>
> I would like to transform the data into new one (sorted by the number of
> years that we observed the ID i)
>
> Id	yr	var1	var2	var3
> 4	1991	3	44	33
> 5	1993	32	33	32
> 2	1992	21	32	32
> 2	1993	32	49	88
> 1	1991	2	3	4
> 1	1992	32	32	22
> 1	1993	32	2	23
> 3	1991	22	32	34
> 3	1992	32	87	76
> 3	1993	33	32	43
>
> I know how to transform to this data in Stata:
>
> sort ID
> by ID: egen pd= count(var1)
> sort pd
> by pd: egen Np= count(pd)
> replace Np= Np/pd
> gsort pd  ID year
>
> But I don't know how to write a program can do this transformation and give
> me pd and Np into vector pd[.,1], Np[.,1], 
> (in this example, pd[]=(1 2 3)' and Np[]=(2 1 2)').And how I can use
> pd[.,1], Np[.,1] to partition 
> the whole transformed matrix [Id yr var1 var2 var3] into blocks(i) [Id yr
> var1 var2 var3] with rows = pd[i,1]*Np[i,1]?
>
> Can someone help me on this problems?
>
> Thank you so much,
> Minh
>
>
>   
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